ISO 29464:2017 空気およびその他のガスの洗浄—用語 | ページ 5

3.1.1

air cleaner

device intended to remove contaminants (3.1.8) from air in a ventilation system or enclosed space

3.1.2

air velocity

rate of air movement

Note 1 to entry: It is expressed in m/s (fpm) to three significant figures.

3.1.3

bypass

air filter bypass

sneakage

proportion of the challenge air stream (3.5.13) that passes around an air cleaner (3.1.1) without interacting with the air cleaner

3.1.4

calibrate

to compare readings from the instrument to be calibrated with those from a reference device

3.1.5

capture

extraction of particles, liquid particles or gases, close to their sources for purposes of collection or sampling

3.1.6

classification

allocation of filters into groups and classes according to relevant aspects of their filtration performance

3.1.7

concentration

quantity of one substance dispersed in a defined amount of another

3.1.8

contaminant

pollutant

substance (solid, liquid or gas) that negatively affects the intended use of a fluid

3.1.9

contamination

pollution

presence of a substance that negatively affects the intended use of a fluid

3.1.10

decontamination factor

ratio of the contaminant (3.1.8) concentration or particle number upstream of the test device to the contaminant concentration (3.1.7) or particle number downstream of the device

Note 1 to entry: The decontamination factor can also be expressed as 1/(1 – overall efficiency) or as 1/penetration.

3.1.11

downstream

area or region into which fluid flows on leaving the test device

3.1.12

efficiency

filter efficiency

fraction or percentage of a challenge contaminant (3.1.8) that is removed by a test device

3.1.13

average efficiency

value of efficiency which results from averaging the efficiencies determined over a number of discreet intervals up to the final pressure differential

3.1.14

effluent

fluid discharged from a given source into the external environment

Note 1 to entry: This is a general term describing any fluid discharged from a given source; in this context, the discharged fluid may be liquid or gaseous and may contain associated liquid and/or particulate contaminants (3.1.8) .

3.1.15

face velocity

filter face velocity

volumetric air flow rate divided by the nominal filter face area (3.1.18)

Note 1 to entry: filter face velocity is expressed in m/s.

3.1.16

filter

air filter

device for separating solid or liquid particles or gaseous contaminant (3.1.8) from an air stream passing through the device

Note 1 to entry: The device is generally formed of a layer or layers of porous, fibrous or granular material.

Note 2 to entry: Air being cleaned by a filter must pass through the filter, whereas an air cleaner (3.1.1) can reduce air contamination (3.1.9) by any method.

3.1.17

filter face area

cross-sectional face area of the filter including the header frame when viewed from the direction of air flow using exact dimensions

3.1.18

nominal filter face area

cross-sectional face area of the filter including the header frame when viewed from the direction of air flow using nominal dimensions

3.1.19

filter insert

replaceable part of a filter which contains the filter medium but which can only operate mounted inside a frame

3.1.20

filter medium

material separating particulate matter (3.2.139) from gases and characterized by its separating structure and its structural and/or textile-technological characteristics

3.1.21

filter medium area

area of filter medium (3.1.20) contained in the filter

Note 1 to entry: For filters with pleats or folds, the filter medium area may be much larger than the filter face area (3.1.17) .

3.1.22

effective filter medium area

effective filtering area

exposed filter area

area of the filter medium (3.1.20) contained in the filter through which air passes during operation

Note 1 to entry: This excludes areas covered by sealant, spacers, struts, etc.

Note 2 to entry: Effective filter medium area is expressed in m².

3.1.23

filter medium velocity

media velocity

medium velocity

volumetric air flow rate divided by the effective filter medium area (3.1.22) of the filter element (3.2.77)

Note 1 to entry: Filter medium velocity is expressed in m/s.

Note 2 to entry: In devices where the filter medium surface area has been increased by use of pleats, folds or bags, the filter medium velocity may be much less than the filter face velocity (3.1.15) .

3.1.24

flow rate

air flow rate

volume of air flowing through the filter per unit time

3.1.25

nominal flow rate

nominal air flow rate

air flow rate specified by the manufacturer

3.1.26

air flow rate, test

test air flow rate

test flow

test flow rate

test volume flow rate

air flow rate used for testing

Note 1 to entry: The flow rate is usually expressed in volumetric units (m³/s).

Note 2 to entry: Test flow rate may differ from the manufacturer’s rated flow through the air cleaner.

3.1.27

rated flow

flow rate through a test device, either as stated by the manufacturer for defined conditions of use or as agreed between the interested parties for a particular installation

Note 1 to entry: The manufacturer’s rated flow may differ from the test air flow rate (3.1.26) .

3.1.28

gas

substance whose vapour pressure is greater than the ambient pressure (3.5.50) at ambient temperature

3.1.29

header frame

integral rigid frame of a filter enabling it to be fastened and sealed against the holding frame (3.1.30)

3.1.30

holding frame

rigid structural frame, part of an air handling system into which filters are fastened and sealed

3.1.31

housing

device used to hold filter

3.1.32

hood

inlet device for extraction system

3.1.33

leak

point in a filter at which the local penetration exceeds a given value

3.1.34

penetration

breakthrough

ratio of contaminant concentration downstream of the test device to the upstream (challenge) concentration (3.1.7)

Note 1 to entry: Sometimes expressed as a percentage.

Note 2 to entry: Penetration is related to efficiency (E) by the expression: E = (1 – P) × 100 %.

Note 3 to entry: Penetration is related to the decontamination factor (DF) (3.1.10) by the expression: DF = 1/penetration.

3.1.35

reference device

primary device possessing accurately known parameters used as a standard for calibrating secondary devices

Note 1 to entry: Reference particle filters are laboratory tested for removal efficiency by particle size (3.2.149) and/or resistance to air flow.

3.1.36

resistance to air flow

differential pressure

pressure differential

pressure drop

difference in absolute (static) pressure between two points in a system

Note 1 to entry: Resistance to air flow is measured in Pa.

3.1.37

test air

air to be used for testing purposes

3.1.38

test device

filter element (3.2.77) being subjected to performance testing

3.1.39

upstream

area or region from which fluid flows as it enters the test device (3.1.38)

3.1.40

washer

dust separator (3.2.158) , droplet separator (3.2.157) or gas purifier (3.5.38) that depends on a liquid acting as a collecting medium for its operation

3.2.1

aerosol

system of solid or liquid particles suspended in gas

Note 1 to entry: In general, one divides the atmospheric aerosol into three size categories: the ultrafine range x < 0,1 µm, the fine range 0,1 µm ≤ x < 1 and the coarse range x ≥ 1 µm, whereby x is the particle diameter (3.2.124) .

3.2.2

liquid phase aerosol

liquid particles suspended in a gas

3.2.3

monodisperse aerosol

aerosol, the width of whose distribution function, described by the geometric standard deviation σg, is less than 1,15 µm

3.2.4

aerosol photometer

light-scattering airborne particle mass concentration (3.1.7) measuring apparatus, which uses a forward-scattering-light optical chamber to make measurements

3.2.5

polydisperse aerosol

aerosol, the width of whose distribution function, described by the geometric standard deviation σg, exceeds 1,5 µm

3.2.6

quasi-monodisperse aerosol

aerosol, the width of whose distribution function, described by the geometric standard deviation σg, is between 1,15 µm and 1,5 µm

3.2.7

reference aerosol

defined approved aerosol for test measurement within a specific size range

3.2.8

solid phase aerosol

solid particles suspended in a gas

3.2.9

test aerosol

aerosol used for determining performance of the device being tested and for calibrating particle measurement devices

3.2.10

agglomerate

collection of solid particles adhering to each other

3.2.11

agglomeration

action leading to the formation of agglomerates (3.2.10)

3.2.12

agglutination

action of joining, by impact (3.2.102) , solid particles coated with a thin adhesive layer or of trapping solid particles by impact on a surface coated with adhesive

3.2.13

aggregate

relatively stable assembly of dry particles, formed under the influence of physical forces

3.2.14

arrestance

measure of the ability of a filter to remove a standard test dust from the air passing through it, under given operating conditions

Note 1 to entry: This measure is expressed as a weight percentage.

3.2.15

average arrestance

ratio of the total amount of loading dust retained by the filter to the total amount of dust fed up to final test pressure differential

3.2.16

average gravimetric arrestance

ratio of the total mass of a standard test dust retained by the filter to the total mass of dust fed up to final test pressure differential

3.2.17

gravimetric arrestance

measure of the ability of a filter to remove mass of a standard test dust from the air passing through it under given operating conditions

Note 1 to entry: This measure is expressed as a weight percentage.

3.2.18

initial arrestance

value of arrestance determined after the first loading cycle in a filter test

Note 1 to entry: For example, in ISO 29461-1 or ISO 16890-3 procedure.

Note 2 to entry: This measure is expressed as a weight percentage.

3.2.19

initial gravimetric arrestance

ratio of the mass of a standard test dust retained by the filter to the mass of dust fed after the first loading cycle in a filter test

Note 1 to entry: This measure is expressed as a weight percentage.

3.2.20

ash

solid residue of effectively complete combustion

3.2.21

fly ash

ash entrained by combustion gases

3.2.22

bioaerosol

particles of biological origin with an aerodynamic diameter of up to 100 μm suspended in a gaseous medium

Note 1 to entry: Bioaerosol particles include viruses, bacteria, fungi, pollen, plant debris, fragments of these and their derivatives such as endotoxins, glucans, allergens and mycotoxins.

3.2.23

burst pressure

value of differential pressure across a filter, above which damage/destruction of the filter medium (3.1.20) or the structure occurs

3.2.24

calibration particle

mono-disperse spherical particle with a known mean particle size, e.g. polystyrene latex (PSL) particle traceable to an international standard of length where the standard uncertainty of the mean particle size is equal to or less than ±2,5 %

Note 1 to entry: The refractive index of (PSL) calibration particles is close to 1,59 at a wavelength of 589 nm (sodium D line).

3.2.25

dust holding capacity

DHC

total weight of loading dust captured by the air-cleaning device up to the final pressure differential

3.2.26

test dust capacity

dust loading capacity

TDC

amount of a standard test dust held by the test device at the final test pressure differential

3.2.27

cleaning

<after clogging> removal of the deposit of solid or liquid particles which has produced clogging

3.2.28

clogging

deposition, progressive or otherwise, of solid or liquid particles on or within a filter medium (3.1.20) , causing the flow to be obstructed

3.2.29

coagulation losses

particle losses due to collision and adhesion of particles

Note 1 to entry: Coagulation affects the measured particle parameters as follows: the particle number concentration (3.2.131) decreases, the particle mass concentration (3.1.7) remains the same and the particle size (3.2.133) increases.

3.2.30

coalescence

action by which liquid particles in suspension (3.2.162) unite to form larger particles

3.2.31

coefficient of variation

cv

standard deviation of a group of measurements divided by the mean

3.2.32

coincidence error

error which occurs because at a given time more than one particle is contained in the measurement volume of a particle counter

Note 1 to entry: The coincidence error leads to a measured number concentration (3.1.7) which is too low and a value for the particle diameter (3.2.124) which is too high.

3.2.33

correlation ratio

calculation of any potential bias between the upstream and downstream sampling systems

3.2.34

correlation ratio

<sampling points>downstream particle concentration divided by the upstream particle concentration (measured without filter)

3.2.35

counting efficiency

expression of that proportion of the particles of detectable size suspended in the volume flow under analysis that make their way through the measured volume and are counted by the particle counter

Note 1 to entry: The counting efficiency depends on the particle size (3.2.133) and decreases progressively in the proximity of the lower detection limit of the particle counter.

3.2.36

counting rate

number of counting events per unit time

3.2.37

cyclone

dust separator (3.2.158) or droplet separator (3.2.157) utilizing essentially the centrifugal force derived from the motion of the gas

3.2.38

DiEthylHexylSebacate

DEHS

liquid used for generating the DEHS test aerosol (3.2.9)

3.2.39

equivalent diameter

diameter of a spherical particle which will give behaviour equivalent to that of the particle being examined

3.2.40

median diameter

diameter of the particle for which the cumulated volume fraction is equal to 50 % on a cumulated volume particle size distribution curve

3.2.41

count median diameter of aerosol

number median diameter of aerosol

CMD

50th percentile of the number distribution of the aerosol

Note 1 to entry: 50 % of the particles are smaller than the count median diameter and 50 % are larger than the count median diameter.

3.2.42

final differential pressure

differential pressure up to which the filtration performance is measured for classification (3.1.6) purposes

3.2.43

initial differential pressure

differential pressure of the clean filter operating at its test air flow rate (3.1.26)

3.2.44

mean differential pressure

arithmetical mean value of the measured number of differential pressures

3.2.45

recommended final differential pressure

maximum operating differential pressure of the filter as recommended by the manufacturer

3.2.46

diluter

dilution system

system for reducing the sampled concentration (3.1.7) to avoid coincidence error in the particle counter

3.2.47

dispersion

operation as a result of which solid particles or liquid particles are distributed in a fluid

Note 1 to entry: Also applied to a two-Phase System in which one phase, known as the “disperse phase”, is distributed throughout the other, known as the “continuous medium”. For example, Dioctyl phthalate (DOP) liquid or liquids with similar physical properties, are dispersed in air to generate a test aerosol (3.2.9) .

3.2.48

D.O.P.

dispersed oil particulates

3.2.49

DOP

dioctyl phthalate

3.2.50

droplet

liquid particle of small mass, capable of remaining in suspension (3.2.162) in a gas

Note 1 to entry: In some turbulent systems, for example clouds, its diameter can reach 200 μm.

3.2.51

dust

airborne solid particles which settle by gravity in calm conditions

3.2.52

dust control

whole of the processes for the separation of solid particles from a gas stream in which they are suspended

Note 1 to entry: By extension, also the activities involved in the construction and commissioning of a dust separator (3.2.158) .

3.2.53

dust feeder

device which is used to distribute test dust to the filter

3.2.54

loading dust

synthetic test dust

synthetic dust formulated specifically for determination of the test dust capacity and arrestance of air filters (3.1.16)

Note 1 to entry: A number of loading dusts are currently in use. Some of them are defined in ISO 15957:2015.

3.2.55

collection efficiency

ratio of the quantity of particles retained by a separator (3.2.156) to the quantity entering it with regard to filters (3.1.16) , dust separators (3.2.158) and droplet separators (3.2.157)

Note 1 to entry: This measure is normally expressed as a percentage.

3.2.56

conditioned efficiency

efficiency of the conditioned filter medium operating at an average medium velocity corresponding to the test air flow rate (3.1.26) in the filter

Note 1 to entry: The conditioning procedure varies depending on the standard being used.

3.2.57

counting efficiency

ratio, expressed as a percentage, of detected number concentration (3.1.7) of particles divided by the actual number concentration of particles in a given size or range of sizes

3.2.58

dust loaded efficiency

efficiency of the filter operating at test flow rate and after dust loadings up to final test pressure differential

3.2.59

fractional efficiency

ability of an air cleaning device to remove particles of a specific size or size range

Note 1 to entry: The efficiency plotted as a function of particle size gives the particle size efficiency spectrum.

3.2.60

initial efficiency

initial particulate efficiency

efficiency of the air cleaning device measured at the start of a performance test while operating at the test air flow rate (3.1.26)

Note 1 to entry: Expressed in % for each selected size of particle.

3.2.61

integral efficiency

overall efficiency

efficiency, averaged over the whole superficial face area of a filter under given operating conditions

3.2.62

local filter efficiency

efficiency at a specific point of a filter element (3.2.77) under given operating conditions

3.2.63

minimum filter efficiency

minimum value of the filter efficiency curve under given operating conditions

3.2.64

particle size efficiency (%)

efficiency for a specific particle diameter

Note 1 to entry: The efficiency plotted as a function of the particle diameter (3.2.124) gives the fractional efficiency curve.

3.2.65

elutriation

method of separating a mixture of particles according to their settling velocities within a fluid

3.2.66

superficial face area

cross-sectional area of the filter element (3.2.77) through which the air flow passes

3.2.67

brush filter

air filter (3.1.16) in which the medium consists of a screen of intermeshing brushes

3.2.68

cartridge filter

compact filter often of cylindrical design

3.2.69

cellular filter

replaceable filter insert (3.1.19) which is or may be installed in a multiple bank or wall structure

Note 1 to entry: Examples of these are HEPA filters (3.2.84) , rigid bags and panels.

3.2.70

ceramic filter

filter with a medium consisting of ceramic fibres or sintered porous ceramic

3.2.71

charged filter

electret filter

filter with an electrostatically charged medium

3.2.72

filter class

range of filtration performances clearly defined by lower and upper limit values

3.2.73

cleanable filter

filter designed to permit the removal of collected dust by application of an appropriate technique

Note 1 to entry: The removal of collected dust is usually partial.

3.2.74

coarse filter

filtration device with particle removal efficiency (3.5.26) < 50 % in the PM₁₀ particle range

3.2.75

disposable filter

filter which is not intended to be cleaned or regenerated for reuse

3.2.76

efficient particulate air filter

EPA filter

filter with performance complying with requirements of classes ISO 15 to ISO 30 as given in ISO 29463-1

3.2.77

filter element

structure made of the filtering material, its supports and its interfaces with the filter housing

3.2.78

fabric filter

filter medium (3.1.20) manufactured either from woven or non-woven textile or a combination of both

Note 1 to entry: The term is most often applied to dust collectors. In these devices the filtering is effectively carried out by a bed of deposited dust, the textile providing a supporting substrate.

3.2.79

fibrous filter

filter comprising a medium consisting of a mass of fibres, including fine and very fine fibres

Note 1 to entry: The efficiency of these filters is derived from the presence of very fine fibres which are supported by coarser fibres in a relatively open structure.

Note 2 to entry: Fibrous filters are usually disposable.

3.2.80

final filter

air filter (3.1.16) used to collect the loading dust passing through or shedding (3.2.159) from the filter under test

3.2.81

fine filter

filtration device with particle removal efficiency ≥50 % in the PM₁₀ particle range

3.2.82

filter group designation

designation of a group of filters (3.2.83) fulfilling certain requirements in the filter classification

Note 1 to entry: ISO 16890-1 defines four groups of filters. Group designations are “ISO coarse”, “ISO ePM10”, “ISO ePM2,5” and “ISO ePM1”.

3.2.83

group of filters

comprises filters of more than one adjacent class within a performance spectrum

3.2.84

HEPA filter

filters with performance complying with requirements of filter class (3.2.72) ISO 35H – ISO 45H per ISO 29463-1

3.2.85

filter installation

filtration devices and systems such as a single filter or a group of filters (3.2.83) mounted together with the same inlet and outlet of air

3.2.86

metal filter

filter with a medium consisting of metal mesh(es), fibres or sintered porous metal

3.2.87

filter pack

filtering material in a preformed shape being a part of a complete filter

3.2.88

panel filter

shallow parallel-faced filter element (3.2.77) or cell

3.2.89

particulate air filter

filter designed to remove suspended particles from air flowing through it

3.2.90

pocket filter

bag filter

filter in which the medium is formed into pockets or bags

3.2.91

renewable media filter

filter in which the medium can be replaced

3.2.92

roll filter

filter incorporating a means for advancing new medium

Note 1 to entry: For example, from a roll.

3.2.93

self-cleaning filter

filter having an inbuilt mechanism for removing collected contaminants (3.1.8)

3.2.94

filter type

designation of the structure and test regime of a filter

3.2.95

ULPA filter

filter with performance complying with the requirements of classes ISO 50 U – ISO 75 U as given in ISO 29463-1

3.2.96

sampling volume flow rate

representative partial flow rate used for the determination of airborne particle characteristics

3.2.97

service flow

gas flow rate through a separator (3.2.156) under given service conditions

3.2.98

folded pack

pack of the filter medium (3.1.20) formed by uniform individual folds

3.2.99

fume

solid aerosol generated by condensation, generally after evaporation from melted substances such as metals and often accompanied by chemical reactions such as oxidation

Note 1 to entry: In popular usage, gaseous effluent, often unpleasant and malodorous, which may arise from chemical processes.

3.2.100

general ventilation

process of moving air from outside the space, recirculated air, or a combination of these into or about a space or removing it from the space

3.2.101

grit

airborne solid particles in the atmosphere or flues

Note 1 to entry: In the UK, defined to be of size greater than 75 μm.

3.2.102

impact

collision of two particles with each other, or of a particle with a solid or liquid surface

3.2.103

impaction

inertial separation due to mass and velocity of a particle causing divergence from the airflow stream lines onto individual filter fibres

3.2.104

isoaxial sampling

sampling in which the flow in the sampler inlet is moving in the same direction as the flow being sampled

3.2.105

isokinetic sampling

technique for air sampling such that the probe inlet air velocity (3.1.2) is the same as the velocity of the air surrounding the sampling point

3.2.106

KCl

solid potassium chloride particles generated from an aqueous solution and used as test aerosol (3.2.9)

3.2.107

measuring procedure with fixed sampling probes

determination of the overall efficiency (3.2.61) using fixed sampling probes upstream and downstream (3.1.11) of the filter being tested

3.2.108

minimum fractional test efficiency

fractional efficiency measured according to ISO 16890-2 after applying the conditioning method defined in this document (also named as “minimum filter efficiency” (3.2.63) or “minimum test efficiency”)

3.2.109

mist

suspension (3.2.162) of droplets in a gas

3.2.110

neutralisation

action of bringing the aerosol to a Boltzmann charge equilibrium distribution with bipolar ions

Note 1 to entry: This process is more often described as"discharging".

3.2.111

particle

small discrete mass of solid or liquid matter

3.2.112

particle bounce

behaviour of particles that impinge on the filter without being retained

3.2.113

particle concentration method

method that can determine the total concentration of particles in the aerosol either by multiple particle counting or chemical concentrations

Note 1 to entry: No particle size classification can be determined by this method.

3.2.114

particle counter

device for detecting and counting numbers of discrete airborne particles present in a sample of air

3.2.115

allowable measurable concentration of the particle counter

fifty percent of the maximum measurable concentration as stated by the manufacturer of the particle counter (3.2.114)

3.2.116

particle counter border zone error

particle sizing error that occurs when particles pass through the optical border of the sensing zone and receive less illumination

Note 1 to entry: The border zone error is device and particle size dependent and has a direct effect on the size resolution.

Note 2 to entry: Due to the border zone error, the particle size (3.2.133) is underestimated.

Note 3 to entry: The larger the particle to be measured, the bigger the border zone error.

3.2.117

particle counter calibration curve

graph depicting the relationship between scattered light intensity and particle size

Note 1 to entry: For the clear particle size and quantity determination, an unambiguous, monotonically increasing calibration curve offers advantages. This enables narrower size intervals to be chosen.

3.2.118

condensation particle counter

CPC

type of optical particle counter (3.2.119) in which very fine airborne particles are enlarged by condensation to a size which may readily be counted by other particle counting methods

Note 1 to entry: It can provide data on particle numbers (3.2.130) but not the original size distribution.

Note 2 to entry: ISO committee dealing with CPC is TC 24/SC 4.

3.2.119

optical particle counter

OPC

particle counter which functions by illuminating airborne particles in a sample flow of air, converting the scattered light impulses to electrical impulse data capable of analysis to provide data on particle population and size distribution

Note 1 to entry: See ISO 21501-4.

3.2.120

particle counter sizing accuracy

Note 1 to entry: x_measured is the particle size indicated by the counter for a reference particle and x_reference is the actual size of the reference particle. Sizes are usually stated in μm.

3.2.121

particle counter sizing resolution

indicates which particle sizes can be differentiated by a particle measuring instrument

3.2.122

particle counter sampling flow rate

particle counter sampling air flow

volumetric flow rate through the instrument

Note 1 to entry: Any error in the volumetric flow rate will affect the reported particle number concentration (3.2.131) .

3.2.123

particle counting and sizing method

particle counting method which allows both the determination of the number of particles and also the classification of the particles according to size

3.2.124

particle diameter

geometric diameter (equivalent spherical, optical or aerodynamic, depending on context) of the particles of an aerosol

Note 1 to entry: Particle diameter is often referred to simply as"particle size".

3.2.125

count mean particle diameter

number mean particle diameter

geometric average of the lower and upper limit of the size range

3.2.126

mean diameter

mean particle diameter

geometric mean of the upper and lower border diameters in a size range

3.2.127

particle flow distribution

distribution of the particle flow over a plane at right angles to the direction of flow

3.2.128

particle flow rate

number of particles that are measured or that flow past a specified cross-section per unit time

3.2.129

particle lower size limit

smallest particle diameter (3.2.124) with a counting efficiency (3.1.12) of 0,5 ± 0,15 (50 % ± 15 %)

3.2.130

particle number

number of particles present in a defined group

3.2.131

particle number concentration

number of particles per unit of volume of air

3.2.132

particle production rate

number of particles produced per unit time by an aerosol generator

3.2.133

particle size

geometric diameter (equivalent spherical, optical or aerodynamic, depending on context) of the particles of an aerosol

3.2.134

particle size analysis

technique used to measure the size distribution of an assembly of particles

3.2.135

particle size distribution

presentation, in the form of tables of numbers or of graphs, of the experimental results obtained using a method or an apparatus capable of measuring the equivalent diameter of particles in a sample or capable of giving the proportion of particles for which the equivalent diameter lies between defined limits

3.2.136

most penetrating particle size

MPPS

particle size (3.2.133) at which the minimum of the particle size efficiency curve occurs under test conditions

Note 1 to entry: This MPPS is dependent on the filter medium (3.1.20) and the test conditions.

3.2.137

particle size range

defined particle counter channel

3.2.138

particle upper size limit

largest particle diameter (3.2.124) with a counting efficiency of 0,5 ± 0,15 (50 % ± 15 %)

3.2.139

particulate matter

PM

solid and/or liquid particles suspended in ambient air

3.2.140

particulate matter efficiency

ePM _x

efficiency (3.1.12) of an air cleaning device to reduce the mass concentration of particles with an optical diameter between 0,3 µm and x µm

3.2.141

particulate matter

PM₁₀

particulate matter (3.2.139) which passes through a size-selective inlet with a 50 % efficiency cutoff at 10 μm aerodynamic diameter

3.2.142

particulate matter

PM_2,5

particulate matter (3.2.139) which passes through a size-selective inlet with a 50 % efficiency cutoff at 2,5 μm aerodynamic diameter

3.2.143

particulate matter

PM₁

particulate matter (3.2.139) which passes through a size-selective inlet with a 50 % efficiency cutoff at 1 μm aerodynamic diameter

3.2.144

porous layer

permeable layer of solid material in any form having interstices of small size, generally known as “pores”

3.2.145

precipitation

operation in which particles are separated from a gas stream in which they are suspended

Note 1 to entry: For example, by the action of an electrical field or a thermal gradient.

3.2.146

electrostatic precipitator

device in which particles become charged and are precipitated on the collecting surface

Note 1 to entry: Also referred to as electrostatic collector, electrical separator or electrostatic separator.

3.2.147

purification

total or partial removal of unwanted constituents from a gaseous medium

3.2.148

re-entrainment

release to the air flow of particles previously collected on the filter

3.2.149

removal efficiency by particle size

ratio of the number of particles retained by the filter to the number of particles measured upstream of the filter for a given particle-size range

3.2.150

final resistance to air flow

resistance to air flow up to which the filtration performance is measured to determine the average arrestance and test dust capacity

Note 1 to entry: Final resistance to air flow is measured in Pa.

3.2.151

initial resistance to air flow

resistance to air flow of the clean filter operating at its test air flow rate (3.1.26)

Note 1 to entry: Initial resistance to air flow is measured in Pa.

3.2.152

recommended final resistance to air flow

maximum operating resistance to air flow of the filter as recommended by the manufacturer

Note 1 to entry: Recommend final resistance to air flow is measured in Pa.

3.2.153

sampling duration

time during which the particles in the sampling volume flow are counted (upstream or downstream (3.1.11) )

3.2.154

scan test

test procedure by which local efficiency or penetration values are determined by sampling filtered air at the downstream filter face according to a specified grid pattern

3.2.155

sedimentation

separation of particles from the fluid in which they are suspended, by the action of gravity

3.2.156

separator

apparatus for separating solid or liquid particles or gases from a gaseous stream in which they are suspended or mixed

Note 1 to entry: A separator (also known as an inertial separator or a collector) takes larger contaminants (3.1.8) out of the air stream, often to prevent them from reaching filters downstream.

3.2.157

droplet separator

apparatus for separating suspended liquid particles from a gas stream

3.2.158

dust separator

apparatus for separating suspended solid particles from a gas stream

3.2.159

shedding

release to the air flow of particles due to particle bounce (3.2.112) and reentrainment effects and to the release of fibres or particulate matter (3.2.139) from the filter or filtering material

3.2.160

smoke

solid or liquid aerosol resulting from combustion of organic materials including fossil fuels, wood and cigarettes

3.2.161

soot

deposits of agglomerated carbonaceous particles formed by incomplete combustion

3.2.162

suspension

two-phase system in which one phase, the disperse phase, is distributed throughout the other, known as the continuous phase

3.2.163

system efficiency

removal efficiency (3.5.26) of a filter system where upstream and downstream particle count measurements may be across several filter banks or other system components

3.2.164

total particle count method

particle counting method in which the total number of particles in a certain sample volume is determined without classification according to size

3.2.165

transmission

ratio of the quantity of particles leaving a filter (3.1.16) , dust separator (3.2.158) or droplet separator (3.2.157) , to the quantity entering it

3.2.166

undersize

percentage of particles smaller than a specified particle size (3.2.133) in a particle size distribution (3.2.135)

Note 1 to entry: Undersize measurement can be particle number (3.2.130) or concentration.

3.2.167

user nominal air volume flow rate

air volume flow rate specified by the user, at which the filter element (3.2.77) is tested in situ

Note 1 to entry: This flow rate may be different from the one specified by the manufacturer.

3.2.168

user nominal filter medium velocity

air volume flow rate specified by the user divided by the effective filter medium area (3.1.22)

3.2.169

zero count rate

number of counts registered per unit time by the particle counter when air, which is free of particles, is passed through the measuring volume

3.3.1

test aerosol

aerosol used for determining the particulate efficiency (3.3.6) of the filter

3.3.2

test air flow rate

volumetric airflow rate used for testing

3.3.3

average gravimetric efficiency

ratio of the total amount of loading dust retained by the filter to the total amount of dust fed up to final test pressure drop (3.3.15)

Note 1 to entry: This definition is the same as the one used for"arrestance, average" in 3.2.

3.3.4

gravimetric efficiency

weighted (mass) removal of loading dust after 50 g of dust load

3.3.5

minimum efficiency

lowest particulate efficiency (3.3.6) of initial, conditioned or dust loaded efficiencies

3.3.6

particulate efficiency

percentage particulate removal efficiency of the filter at specified particle sizes measured with a particle counter in the range of 0,3 µm to 3,0 µm

3.3.7

depth loading filter

filter in which particles penetrate into the filter medium (3.1.20) and are collected on the fibres in the depth of the filter medium

3.3.8

low efficiency filter

air filter (3.1.16) with an initial particulate efficiency (3.2.60) at 0,4 µm particles in the range E < 35 %

3.3.9

medium efficiency filter

air filter (3.1.16) with an initial particulate efficiency (3.2.60) at 0,4 µm particles in the range 35 % ≤ E ≤ 85 %

3.3.10

high efficiency filter

air filter (3.1.16) with an initial particulate efficiency (3.2.60) at 0,4 µm particles in the range E ≥ 85 %

3.3.11

pulse jet filter

cleanable air filter, that typically is cleaned with air jet pulses to provide a longer service life

3.3.12

static filter

air filter (3.1.16) that will be removed (exchanged) after it has reached its final test pressure drop (3.3.15) and that is not cleaned with jet pulses or other means in order to fully or partially, retrieve its initial performance (pressure drop and efficiency)

3.3.13

surface loading filter

filter in which the dust is collected on the surface of the filter medium (3.1.20)

3.3.14

untreated filter

air filter not submitted to conditioning

3.3.15

final test pressure drop

maximum pressure drop of the filter up to which the filtration performance is measured

3.3.16

recommended final test pressure drop

maximum operating pressure drop of the filter as recommended by the manufacturer at rated airflow

3.3.17

initial pressure drop

pressure drop of the clean filter operating at the test airflow rate

3.4.1

aged flat filter sheet

flat filter sheet exposed under simulated hot and corrosive gas (3.4.7) conditions for a preset period of time to evaluate the change of filtration properties

3.4.2

air permeability

gas volume flow rate per unit filtration area at pressure drop of 124,5 Pa

3.4.3

average gas concentration

mean concentration of test gases (3.4.26) during the exposure (3.6.4)

3.4.4

batch type exposure chamber

chamber in which filter sheets are exposed to stationary test gas (3.4.26) mixture

3.4.5

chemical degradation

degradation (3.4.8) of chemical properties of filter media by the interaction with test gas (3.4.26)

3.4.6

continuous-flow-method

method of exposing a filter sheet in a continuous flow of test gas (3.4.26) mixture

3.4.7

corrosive gas

chemical which reacts with filter medium (3.1.20) and change its chemical and physical properties

3.4.8

degradation

change in physical and chemical performance of a filter medium (3.1.20) caused by interaction with corrosive gases (3.4.7)

3.4.9

elongation

incremental change in length of test specimen determined by tensile test

3.4.10

elongation at maximum load

incremental change in length of test specimen at maximum load determined by tensile test

3.4.11

elongation ratio

ratio of elongation (3.4.9) of test specimen to its initial length between holders (3.4.16)

Note 1 to entry: It can be expressed as a percentage.

3.4.12

elongation ratio at maximum load

ratio of elongation (3.4.9) of test specimen at maximum load in tensile test to its initial length between holders (3.4.16)

3.4.13

exposure chamber

chamber to expose test filter sheet to corrosive gases (3.4.7)

3.4.14

flow-through type replacement

method to replace test gas in the batch type exposure chamber (3.4.4) by introducing test gas (3.4.26) continuously to the chamber

3.4.15

initial load

load applied to the test specimen at the start of tensile test

3.4.16

length between holders

length between the jaws of the top and bottom holding chucks as positioned at the start of the tensile test

3.4.17

load

tensile strength (3.4.25) of test specimen observed in the tensile test

3.4.18

non-continuous-flow-method

method of exposing a filter sheet in a stationary test gas (3.4.26) mixture

3.4.19

nonwoven fabric

filter medium (3.1.20) manufactured using fabric made from long fibres bonded together with each other by chemical, mechanical, heat or solvent treatment

3.4.20

number of replacement

number of test gas (3.4.26) replacement for whole heating space volume of the test chamber

3.4.21

replacement of gas

exchange gas to maintain test gas (3.4.26) concentration within certain concentration range

3.4.22

retention of tensile strength

ratio of tensile strength (3.4.25) of the test specimen subjected to thermal and/or acid gas exposure to that of the test specimen without the exposure (3.6.4)

3.4.23

strip method

method of implementing tensile test with holding whole width of the test specimen with a holding device

3.4.24

tensile speed

speed to pull a test specimen in tensile test

3.4.25

tensile strength

value of the maximum load (3.4.17) divided by the width of test specimen

3.4.26

test gas

gas which may cause changes in physical properties of filter media to be used for tensile test

3.4.27

thermal exposure

exposure (3.6.4) of filter medium to an elevated temperature to accelerate the change in its physical properties

3.4.28

vacuum replacement

method to replace test gas (3.4.26) in the batch type exposure chamber (3.4.4) by the use of vacuum

3.4.29

woven fabric

filter medium (3.1.20) manufactured using a fabric formed by weaving

3.5.1

absorption

the transport and dissolution of a sorbate into an absorbent to form a mixture having the characteristics of a solution

3.5.2

active site

position on an adsorbent (3.5.4) surface with the potential to trap an adsorbate (3.5.3) molecule

3.5.3

adsorbate

molecular compound in gaseous or vapour phase that may be retained by an adsorbent (3.5.4) medium

3.5.4

adsorbent

material having the ability to retain gaseous or vapour contaminants (3.1.8) on its surface by physical or chemical processes

3.5.5

regenerable adsorbent

adsorbent (3.5.4) material which, after saturation, may be treated to recover its adsorption properties thereby enabling its reuse

3.5.6

ageing of adsorbent

chemical or physical process which reduces the effectiveness (efficiency and/or capacity) of an adsorbent (3.5.4)

Note 1 to entry: Ageing reduces the number of active sites (3.5.2) .

3.5.7

adsorption

process in which the molecules of a gas or vapour adhere by physical or chemical processes to the exposed surface of solid substances, both the outer surface and inner pore surface, with which they come into contact

3.5.8

activated alumina

aluminium oxide, usually in the form of granules, treated to enhance its surface area and consequent ability to adsorb gases

3.5.9

bed depth

depth of the adsorbent (3.5.4) medium through which the gas being processed passes

Note 1 to entry: See 3.1.34.

3.5.10

breakthrough time

time to reach a specified penetration (x)

Note 1 to entry: Relevant breakthrough times may be defined as penetrations of 5 %, 50 % and 95 % (tb5, tb50, tb95)

Note 2 to entry: Breakthrough time is sometimes referred to as breakthrough point.

3.5.11

breakthrough vs. time curve

plot of contaminant (3.1.8) penetration versus time for a particular challenge concentration (3.5.14) and airflow

3.5.12

adsorbate capacity

amount (mass or moles) of a selected adsorbate (3.5.3) that can be contained in the GPAC Medium or Device under given test conditions and end point (termination time)

Note 1 to entry: Capacity can also be negative during desorption (3.5.21) .

3.5.13

challenge air stream

test contaminant(s) (3.1.8) of interest diluted to the specified concentration(s) of the test prior to filtration

3.5.14

challenge concentration

concentration of the test contaminant(s) (3.1.8) of interest in the air stream prior to filtration ( challenge air stream (3.5.13) )

3.5.15

challenge compound

chemical compound that is being used as the contaminant (3.1.8) of interest for any given test

3.5.16

channelling

disproportionate or uneven flow of gas through passages of lower resistance due to inconsistencies in the design or production of a GPACD, particularly in packed granular beds

3.5.17

activated charcoal

activated carbon

carbon, usually in the form of granules, treated to enhance its surface area and consequent ability to adsorb gases through a highly developed pore structure

Note 1 to entry: Usually produced from coal, carbonized coconut shell or other organic materials.

3.5.18

chemisorption

chemical adsorption

trapping of gaseous or vapour contaminants on an adsorbent (3.5.4) involving chemical reaction on the adsorbent surface

3.5.19

close valve time

time when the challenge gas(es) are initially turned off or when switching from upstream to downstream monitoring

3.5.20

decay time

time required for the gas contaminant monitoring instrument to record a reduction from an initial value greater than 95 % of the challenge concentration (3.5.14) to a final value of less than 5 % of the challenge concentration at the downstream sampling point for a specific test, challenge gas and gas flow, after stopping the injection of the contaminant (3.1.8) with no GPAC Media or Device present

3.5.21

desorption

process in which adsorbate (3.5.3) molecules leave the surface of the adsorbent (3.5.4) and reenter the air stream

Note 1 to entry: Desorption is the opposite of adsorption.

3.5.22

efficiency vs. capacity curve

plot of the GPACD removal efficiency (3.5.26) against the integrated capacity over the duration of a challenge test for a particular challenge concentration (3.5.14) and airflow

3.5.23

efficiency vs. time curve

plot of the GPAC Medium or Device removal efficiency (3.5.26) against time over the duration of a challenge test for a particular challenge concentration (3.5.14) and airflow

3.5.24

end efficiency

removal efficiency (3.5.26) calculated from the concentrations at the end of the test

3.5.25

initial efficiency

efficiency of an unexposed filter or GPACD calculated as soon after the start of a test as is possible

3.5.26

removal efficiency

fraction or percentage of a challenge contaminant that is retained by a GPAC Medium or Device at a given time

Note 1 to entry: Removal efficiency is also known simply as"efficiency".

3.5.27

carbon filter

filter in which the filtering medium is, or includes, activated charcoal (3.5.17) and which is used for the separation of gaseous substances from the passing air

3.5.28

sorption filter

filter that removes gases or vapour contaminants from a gas stream using adsorption or absorptive processes

3.5.29

filtration

separation of contaminants (3.1.8) from a fluid stream in which they are suspended through retention of the contaminants (by extension, also the whole of the activities involved in the construction and commissioning of a filter installation (3.2.85) )

3.5.30

flow rate sampling point

location where the air flow rate is sufficiently stable to permit a reliable flow measurement

3.5.31

test volume flow rate

volumetric air flow rate used for testing

3.5.32

gas phase air cleaning device

GPACD

assembly of a fixed size enabling the removal of specific gas- or vapour-phase contaminants

Note 1 to entry: It is normally box shaped or fits into a box of dimensions between 300 mm × 300 mm × 300 mm up to approximately 610 mm × 610 mm × 610 mm or 2 ft × 2 ft × 2 ft.

3.5.33

GPAC medium or device face area

cross-sectional area of the GPAC Medium or Device also including a header frame or other support structures if so equipped when viewed from the direction of air flow using exact dimensions

3.5.34

gas phase air cleaning medium

GPACM

solid medium or medium configuration used for filtering a contaminant (3.1.8)

3.5.35

GPACM-LF

adsorbent (3.5.4) in the form of particles of different shape and size intended for e.g. loose fill applications

3.5.36

GPACM-FL

adsorbent (3.5.4) in the form of flat sheet that is flexible, thin and nominally 2-dimensional

3.5.37

GPACM-TS

adsorbent (3.5.4) in the form of a three-dimensional structure that is many times thicker than flat sheet and used as a finished element in a device

3.5.38

gas purifier

apparatus for totally or partially removing one or more constituents from a gas mixture

3.5.39

lag time

rise time

time between initial injection of contaminant (3.1.8) and reaching 95% of the challenge concentration (3.5.14) for an empty duct measured at the downstream sampling location

Note 1 to entry: Lag/rise time is specific to a particular test, challenge gas and gas flow rate.

3.5.40

molecular contamination

contamination (3.1.9) present in gas or vapour phase in an air stream and excluding compounds in particulate (solid) phase regardless of their chemical nature

3.5.41

molecular sieve

silica-based mineral having a crystalline three-dimensional structure with cavities and channels whose surfaces can adsorb small molecules

3.5.42

open valve time

time at which challenge contaminants are initially injected into the test duct

3.5.43

ppb(v)

parts per billion by volume concentration measure normally used to record ambient levels of outdoor pollution

Note 1 to entry: Units are mm³/m³.

3.5.44

ppm(v)

parts per million by volume concentration measure normally used to record pollution levels in, e.g. work place safety

Note 1 to entry: Units are cm³/m³ and ml/m³.

3.5.45

physisorption

physical adsorption

attraction of an adsorbate (3.5.3) to the surface, both outer surface and inner pore surface, of an adsorbent (3.5.4) by physical forces (Van der Waals forces)

3.5.46

pores

minute passageways through which fluid may pass or that expose to the fluid stream the internal surfaces of an adsorbent (3.5.4) medium

3.5.47

macro-pores

largest sized pores (3.5.46) (diameter > 50 nm) of adsorbent (3.5.4) media

3.5.48

meso-pores

intermediate sized pores (3.5.46) (diameter > 2 nm and < 50 nm) of adsorbent (3.5.4) media

3.5.49

micro-pores

smallest sized pores (3.5.46) (diameter < 2 nm) of adsorbent (3.5.4) media

3.5.50

ambient pressure

absolute pressure immediately outside the test rig

3.5.51

purge time

time required for the contaminant sampling system and monitoring instrument to register a change from an initial value lower than 1 % of the challenge concentration (3.5.14) to a final value greater than 95 % of the challenge concentration (or vice versa), as when a single instrument is switched from upstream to downstream monitoring and back

3.5.52

residence time

relative time that an increment of fluid [or contaminant (3.1.8) ] is within the boundaries of the medium volume

Note 1 to entry: An example of the medium volume is a bed of granules or a non-woven sheet.

Note 2 to entry: In typical use and in this document, this value neglects the fact that the medium and possible support structures occupy a significant portion of the volume of the bed (residence time is calculated as total bed volume/air flow rate).

3.5.53

retentivity

measure of the ability of an adsorbent (3.5.4) or GPACD to resist desorption (3.5.21) of an adsorbate (3.5.3)

Note 1 to entry: Computed as the residual capacity (fraction remaining) after purging the adsorbent with clean, conditioned air only, following challenge breakthrough.

3.5.54

separator

apparatus for separating solid or liquid particles or gases from a gaseous stream in which they are suspended or mixed

3.5.55

sorbates

molecular compounds that are retained in the adsorbent (3.5.4) of the device

Note 1 to entry: The sorbate will refer to both intended compounds like the selected challenge gas in a test or pollution in real service but also any other compounds present in the air stream, e.g. gases and vapours (3.5.61) .

3.5.56

sorption

process in which fluid molecules (gas or liquid) are removed by the GPACM by absorption (3.5.1) or adsorption

3.5.57

space velocity

measure of residence time (3.5.52) of the airflow to pass through the adsorbent (3.5.4) bed

Note 1 to entry: Space velocity = (residence time)⁻¹.

3.5.58

test end time

time when a desired concentration or other termination criteria have been met in any of the prescribed test procedures

Note 1 to entry: See also the definition for breakthrough time, 3.5.10.

3.5.59

test start time

time when contaminant concentration upstream equals the challenge concentration (3.5.14) for an empty duct

3.5.60

transit time

gas or vapour (3.5.61) flow time to pass through the sorbent

Note 1 to entry: Transit time is calculated by dividing the sorbent volume by the air flow rate.

3.5.61

vapour

substance whose vapour pressure is less than the ambient pressure (3.5.50) at ambient temperature, but is present in the gas phase through evaporation or sublimation

3.5.62

zeolite

aluminium silicate granules or pellets having an open lattice structure with pores (3.5.46) running through them which can trap small molecules

3.6.1

cutaneous damage

any damage to the skin, particularly that caused by exposure (3.6.4) to UVC energy

3.6.2

disinfection

less lethal process of inactivating microorganisms compared to sterilization

3.6.3

erythema

reddening of the skin, with or without inflammation, caused by the actinic effect of solar radiation or artificial optical radiation

3.6.4

exposure

subjection to infectious agents, irradiation, particulates or chemicals that could have harmful effects

3.6.5

fluence rate

fluence across a surface

Note 1 to entry: Fluence rate is expressed in J/m², J/cm², or W·s/cm².

3.6.6

in-duct systems

UVC lamp devices placed up-stream or down-stream of the cooling coil or in other enclosed sections of the HVAC duct system

3.6.7

irradiance

power of electromagnetic radiation incident on a surface per unit surface area

Note 1 to entry: Irradiance is expressed in microwatts per square centimetre (μW/cm²).

3.6.8

effective irradiance

power of UVC radiation from electromagnetic radiation received on a surface per unit surface area

3.6.9

ocular damage

any damage to the eye, particularly that caused by exposure (3.6.4) to UV energy

3.6.10

permissible exposure time

PET

calculated time period that humans, with unprotected eyes and skin, can be exposed to a given level of UV irradiance without exceeding the NIOSH recommended exposure limit (REL) or ACGIH Threshold Limit Value^® (TLV^® ) (3.6.17) for UV radiation

3.6.11

personal protective equipment

PPE

equipment used to shield or insulate a person from chemical, physical or thermal hazard

Note 1 to entry: Equipment includes protective clothing, helmets, goggles, respirators and other gear.

3.6.12

photokeratitis

corneal inflammation after over exposure (3.6.4) to ultraviolet radiation (3.6.18)

3.6.13

photokeratoconjunctivitis

inflammation of cornea and conjunctiva after exposure (3.6.4) to UV radiation (3.6.18)

Note 1 to entry: Exposure to wavelengths shorter than 320 nm is most effective in causing this condition. The peak of the action spectrum is approximately 270 nm.

3.6.14

portable in-room disinfection UVC device

easy-to-carry equipment to use in spaces requiring ultraviolet ray disinfection (3.6.2)

3.6.15

radiometer

instrument used to measure radiometric quantities, particularly UV irradiance or fluence

3.6.16

stratum corneum

outer dead layer of human skin

3.6.17

Threshold Limit Value^®1

TLV^®

guidelines on exposure level under which most people can work consistently for eight hours a day, day after day, without adverse effects

Note 1 to entry: Used by the ACGIH to designate degree of exposure (3.6.4) to contaminants (3.1.8) .

Note 2 to entry: TLVs can be expressed as approximate milligrams of particulate per cubic metre of air (mg/m³). TLVs are listed either for 8 h as a time-weighted average (TWA) or for 15 min as a short-term exposure limit (STEL).

3.6.18

ultraviolet radiation

UV radiation

wavelength of the electromagnetic spectrum of radiation from 10 nm to 400 nm

Note 1 to entry: The range between 100 nm and 400 nm is commonly subdivided into: — UVA: 315 nm to 400 nm; — UVB: 280 nm to 315 nm; — UVC: 200 nm to 280 nm; — Vacuum UV: 100 nm to 200 nm.

3.6.19

UV dose

product of UV irradiance and specific exposure time on a given microorganism or surface

Note 1 to entry: UV dose is expressed in millijoules per square centimetre (mJ/cm²).

3.6.20

ultraviolet germicidal irradiation

UVGI

method for disinfection (3.6.2) of air, water and surfaces that uses radiation with wavelength (3.6.23) in the range 240 nm to 280 nm to kill or inactivate micro-organisms

3.6.21

upper-air in-room systems

UVC lamp devices mounted underneath room ceilings with UVC energy directed upward with adjustable louvers to keep UVC rays above eye and head level

3.6.22

waveband

spectrum section

spectrum band

electromagnetic spectrum that is usually divided into a large spectral region, small spectral band and narrow spectral lines

Note 1 to entry: Waveband is commonly expressed as a specific wavelength (3.6.23) range of values, which sometimes uses numbers or letters as code.

3.6.23

wavelength

distance between repeating units of a wave pattern

Note 1 to entry: Commonly designated by the Greek letter lambda (λ).