SIST-TP CEN/TR 16013-1:2010
(Main)Workplace exposure - Guide for the use of direct-reading instruments for aerosol monitoring - Part 1: Choice of monitor for specific applications
Workplace exposure - Guide for the use of direct-reading instruments for aerosol monitoring - Part 1: Choice of monitor for specific applications
This Technical Report describes the principles underlying the evaluation of one or more aerosol fractions using direct-reading aerosol monitors. The currently available methods for monitoring levels of aerosols in workplaces for a range of different purposes are described and details are given of their limits and possibilities in the field of occupational hygiene. The document does not cover the sampling of aerosols for compliance with occupational exposure limits or the collection of aerosol particles for subsequent analysis.
Exposition am Arbeitsplatz - Leitfaden für die Anwendung direkt anzeigender Geräte zur Überwachung von Aerosolen - Teil 1: Auswahl des Monitors für besondere Anwendungsfälle
Exposition au poste de travail - Guide d'utilisation des instruments à lecture directe pour la surveillance des aérosols - Partie 1: Choix du moniteur pour des applications spécifiques
Le présent Rapport Technique du CEN décrit les principes de l’évaluation d’une ou plusieurs fractions
d’aérosols à l’aide de moniteurs d’aérosols à lecture directe. Les méthodes actuellement disponibles pour
surveiller les concentrations d’aérosols sur les lieux de travail à diverses fins sont décrites et leurs limites et
possibilités dans le cadre de l’hygiène du travail sont précisées.
Le présent document ne traite pas du prélèvement des aérosols pour la conformité aux valeurs limites
d’exposition professionnelle ou de la collecte des particules d’aérosols pour une analyse ultérieure.
Izpostavljenost na delovnem mestu - Vodilo za uporabo instrumentov z neposrednim odčitavanjem za monitoring aerosolov - 1. del: Izbira instrumenta za specifične uporabe
To tehnično poročilo opisuje načela, ki so podlaga za vrednotenje ene ali več aerosolnih frakcij z neposrednim odčitavanjem za monitoring aerosolov. Opisane so trenutno razpoložljive metode za monitoring ravni aerosolov na delovnih mestih za vrsto različnih namenov, prav tako pa so podane podrobnosti o njihovih omejitvah ter možnostih na področju higiene pri delu. Ta dokument ne zajema vzorčenja aerosolov za ugotavljanje izpolnjevanja omejitev izpostavljenosti na delovnem mestu ali zbiranje aerosolnih delcev za nadaljnjo analizo.
General Information
Standards Content (Sample)
SLOVENSKI STANDARD
SIST-TP CEN/TR 16013-1:2010
01-november-2010
,]SRVWDYOMHQRVWQDGHORYQHPPHVWX9RGLOR]DXSRUDERLQVWUXPHQWRY]
QHSRVUHGQLPRGþLWDYDQMHP]DPRQLWRULQJDHURVRORYGHO ,]ELUDLQVWUXPHQWD]D
VSHFLILþQHXSRUDEH
Workplace exposure - Guide for the use of direct-reading instruments for aerosol
monitoring - Part 1: Choice of monitor for specific applications
Exposition am Arbeitsplatz - Leitfaden für die Anwendung direkt anzeigender Geräte zur
Überwachung von Aerosolen - Teil 1: Auswahl des Monitors für besondere
Anwendungsfälle
Exposition au poste de travail - Guide d'utilisation des instruments à lecture directe pour
la surveillance des aérosols - Partie 1: Choix du moniteur pour des applications
spécifiques
Ta slovenski standard je istoveten z: CEN/TR 16013-1:2010
ICS:
13.040.30 Kakovost zraka na delovnem Workplace atmospheres
mestu
SIST-TP CEN/TR 16013-1:2010 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
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SIST-TP CEN/TR 16013-1:2010
TECHNICAL REPORT
CEN/TR 16013-1
RAPPORT TECHNIQUE
TECHNISCHER BERICHT
May 2010
ICS 13.040.30
English Version
Workplace exposure - Guide for the use of direct-reading
instruments for aerosol monitoring - Part 1: Choice of monitor for
specific applications
Exposition au poste de travail - Guide d'utilisation des Exposition am Arbeitsplatz - Leitfaden für die Anwendung
instruments à lecture directe pour la surveillance des direkt anzeigender Geräte zur Überwachung von Aerosolen
aérosols - Partie 1: Choix du moniteur pour des - Teil 1: Auswahl des Monitors für besondere
applications spécifiques Anwendungsfälle
This Technical Report was approved by CEN on 13 March 2010. It has been drawn up by the Technical Committee CEN/TC 137.
CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland,
Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2010 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TR 16013-1:2010: E
worldwide for CEN national Members.
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Contents Page
Foreword .3
Introduction .4
1 Scope .6
2 Abbreviations .6
3 Principles of direct-reading aerosol monitoring methods .6
3.1 General .6
3.2 Vibrational mass methods .7
3.2.1 Piezoelectric mass monitors .7
3.2.2 TEOM − Tapered Element Oscillating Microbalance .9
3.3 Beta mass monitors . 12
3.3.1 Operating principle . 12
3.3.2 Determination of mass concentration of health-related fractions . 14
3.3.3 Calibration of beta mass monitors. 14
3.3.4 Advantages and disadvantages . 14
3.3.5 Currently available beta mass monitors . 15
3.4 Methods of optical measurement of aerosols . 16
3.4.1 General . 16
3.4.2 Photometers . 16
3.4.3 Optical particle counters . 20
4 Requirements for different applications of direct-reading dust monitors . 23
4.1 General . 23
4.2 Walk through surveys . 23
4.3 Identification of main process or source emitting aerosols . 23
4.4 Use with video visual techniques . 23
4.5 Assessing efficiency of control systems . 24
4.6 Watchdogs to monitor levels in workplaces and ensure controls are working . 24
4.7 Surrogate personal exposure assessment . 24
Bibliography . 25
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Foreword
This document (CEN/TR 16013-1:2010) has been prepared by Technical Committee CEN/TC 137
“Assessment of workplace exposure to chemical and biological agents”, the secretariat of which is held by
DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
CEN/TR 16013, Workplace exposure — Guide for the use of direct-reading instruments for aerosol
monitoring, consists of the following parts:
Part 1: Choice of monitor for specific applications
Part 2: Evaluation of airborne particle concentrations using Optical Particle Counters
Part 3: Evaluation of airborne particle concentrations using photometers (in preparation)
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Introduction
The assessment of aerosols in the workplace can have several aims, including:
a) estimation of the mean concentration of health-related aerosol particles (see EN 481) during a working
shift period (workplace characteristics or personal exposure by static or personal sampling);
b) sampling to provide a sample of airborne particles for later analysis (gravimetric, morphological, chemical,
physical, mineralogical, etc., see EN 482);
c) evaluation of almost instantaneous concentrations produced by various work activities using automatic
instruments (photometers,β -attenuation instruments, vibrational mass balance instruments);
d) evaluation of almost instantaneous concentrations and particle size distributions (optical particle
counters – OPC).
This Technical Report concerns items c) and d), gives the principles, and details the general conditions to be
satisfied. In occupational hygiene, no measurement procedure recommends exposure monitoring using direct-
reading aerosol monitors. These instruments should instead be considered as permitting a complementary
approach to the conventional filter-based gravimetric method. The different types of information obtained are
explained in Figure 1.
a) b)
Key
X sample number (time) Y concentration (arb units)
Figure 1 ― Information from integrated filter sampling vs. continuous monitoring
There is a wide range of portable and personal direct-reading aerosol monitors available.
Recent advances in modern electronics and battery technology means direct-reading dust monitors are
becoming smaller and lighter and of relatively low price. In addition to reliance on compliance with
Occupational Exposure Limits, emphasis is now also being placed on control banding and advice on suitable
control systems. This has led to new roles being identified for direct-reading aerosol monitors in ensuring that
systems deployed to control exposure to airborne dusts actually work. Some types of direct-reading aerosol
monitors appear to be well suited to evaluate prevention action efficiency and to space- and time-related
monitoring of concentration.
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All instruments mentioned in this document (see, in particular, Tables 2, 4, 6, 8 and 10) are examples of
suitable products available commercially. This information is given for the convenience of users of this
Technical Report only and does not constitute an endorsement by CEN of these products.
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1 Scope
This Technical Report describes the principles underlying the evaluation of one or more aerosol fractions
using direct-reading aerosol monitors. The currently available methods for monitoring levels of aerosols in
workplaces for a range of different purposes are described and details are given of their limits and possibilities
in the field of occupational hygiene.
The document does not cover the sampling of aerosols for compliance with occupational exposure limits or
the collection of aerosol particles for subsequent analysis.
2 Abbreviations
For the purposes of this document, the following abbreviations apply.
DRAM direct-reading aerosol monitor
LOD limit of detection
OEL occupational exposure limit
OPC optical particle counter
PM particulate matter
TEOM tapered element oscillating microbalance
TSP total suspended particulate
3 Principles of direct-reading aerosol monitoring methods
3.1 General
There are many methods, based on different physical principles, for the instantaneous measurement of
aerosols. Instruments used are generally called direct-reading or continuous monitoring instruments.
Depending on their design, they can give the instantaneous or sequential concentration and can sometimes
even measure particle size distribution.
Instantaneous measurement has several advantages:
a) immediate knowledge of the result without going through the laboratory, whence the possibility of rapid
intervention (e.g. implementation of a ventilation system);
b) continuous measurement, long-distance surveillance, concentration record over time, mean concentration
integration and calculation in selected periods, maxima and minima determination, source location, etc.;
c) measurement of concentration for particles of unstable composition (e.g. volatile substances);
d) monitoring and control of aerosol concentration.
Depending on the principles used, automatic methods can be classed into the following three main groups:
vibrational mass method (see 3.2);
beta attenuation method (see 3.3);
optical methods (see 3.4).
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3.2 Vibrational mass methods
3.2.1 Piezoelectric mass monitors
3.2.1.1 Operating principle
Particles drawn into the instrument are collected on the surface of a piezoelectric crystal, forming part of a
quartz crystal-based oscillating circuit (see Figure 2).
Key
1 piezoelectric crystal
2 frequency
Figure 2 ― Schematic of piezoelectric mass monitor
The mass of deposited particles causes a reduction in the oscillation frequency f. The changed frequency is
compared with the previous recorded initial frequency or a control circuit frequency. The frequency reduction
is directly proportional to the particle mass (see [8]). The proportionality factor k expresses the crystal
f
sensitivity with respect to the deposited weight. It is constant for each crystal (see [7]) and its value varies, in
most cases, by approximately 200 Hz/µg. If the frequency change during sampling, for a time t, is ∆f, the
∆f
weight of collected dust will be and the aerosol mean concentration can be calculated according to
k
f
Equation (1):
∆f
C = (1)
Q× t × k
s f
where
C is the aerosol mean concentration, in milligrams per cubic metre;
∆f is the change resonance frequency, in Hertz;
Q is the sampling flow rate, in litres per minute;
t is the sampling time, in minutes;
s
k is the crystal mass sensitivity, in Hertz per microgram
f
The method is very sensitive and allows low concentrations of the order of several tens of micrograms per
cubic metre to be measured. However, it is limited to fine particles (usually smaller than 10 µm) because of
the small mechanical force between the particle and the crystal surface: if its mass is high, the particle cannot
follow the vibration frequency. This is also a problem for high loads when there is lack of coupling between the
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outermost layers of particles and the crystal. This requires the crystal to be regularly cleaned and may limit the
monitoring duration.
3.2.1.2 Determination of mass concentration of health-related fractions
The change in frequency of crystal is directly proportional to the mass of particles deposited and is therefore
largely independent of the physical and chemical properties of the particles. There is no need therefore to use
on-site calibration factors, providing that the crystal is not overloaded. Because of particle size limitations on
particle/sensor coupling (mentioned above) only the mass concentration of the respirable fraction is
measurable. Respirable size selection can be achieved using any suitable size selector; one instrument uses
a single stage impactor with the respirable particles deposited on the crystal by electrostatic precipitation.
Another instrument uses multiple crystals as the collection substrate for size separated particles in a 10-stage
cascade impactor.
3.2.1.3 Calibration of piezoelectric instruments
Each crystal sensor has its own frequency response and so the instrument incorporating the crystal will be
calibrated in the factory to give the required mass response. Provided that the crystal is not damaged, no
further calibration is required.
3.2.1.4 Advantages/disadvantages of piezoelectric instruments
Table 1 gives advantages and disadvantages of piezoelectric instruments.
Table 1 ― Advantages/disadvantages of piezoelectric instruments
Advantages Disadvantages
direct measurement of dust mass usage limited by dust loading on crystal
no on-site calibration required regular cleaning of crystal required
response independent of chemical only suitable for respirable particles
composition and particle size
(below 10 µm)
relatively easy to use
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3.2.1.5 Currently available piezobalance instruments
Table 2 gives an overview on currently available piezobalance instruments.
Table 2 ― Currently available piezobalance instruments
a
Name Portable/ Size Weight Size Flow Response Accuracy Measure-
personal selection rate time ment range
3
mm kg l/min s mg/m
3
Kanomax portable 311 × 170 × 130 2 respirable 1 from 0 mg/m ± 10 % of 0,02 to 10
3
Piezo- fraction by to 1 mg/m : reading
balance impactor 24 s
dust
from
monitor
3
> 1 mg/m
Model
3
to 10 mg/m :
®
3511
120 s
California portable, cascade 5,4 10 stages 2 for average not given 0,005 to 1
Measure- but impactor: concentration
(0,1 µm to
3
ments mains- 35 × 12,5 × 32 0,05 mg/m :
14 µm)
Inc, PC- operated 30 s
control unit: 10
2HX
18 × 43 × 32
®
QCM (battery-
real-time powered
cascade version
impactor by
special
order)
NOTE "Accuracy" is defined by the manufacturers.
® ®
a
Kanomax Piezo-balance dust monitor Model 3511 and California Measurements Inc, PC-2HX QCM real-time cascade impactor are
examples of suitable products available commercially. This information is given for the convenience of users of this Technical Report
and does not constitute an endorsement by CEN of these products.
3.2.2 TEOM − Tapered Element Oscillating Microbalance
3.2.2.1 Operating principle
This device is similar in principal to the piezoelectric microbalance but the oscillating frequency is applied to a
tapered glass tube equipped with sampling filter at its narrow end (see Figure 3).
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Key
1 filter
2 tapered glass tube
f frequency
Figure 3 ― Schematic of the TEOM device
The 13 mm diameter filter responsible for collecting the sampled aerosol particles is held inside a plastic
cassette that is a close push-fit to the glass tube. The top part of the tapered tube is coated with an electrically
conducting layer and it is placed between two flat electrodes, which maintain a continuous electric field. An
oscillating current flows through the conducting layer, prompting vibration of the tapered tube. The vibration
frequency is measured by an optical system comprising an LED photo-emitting diode and a phototransistor.
The pulsating current linked to the tapered tube oscillations is amplified and returned to the conducting layer,
thereby creating a closed loop system. At equilibrium, the electrical oscillation frequency is equal to the
tapered tube's natural mechanical vibration frequency. This frequency depends on the mass of the filter
cassette positioned at the narrow end of the tube and, thus, on the mass of deposited particles, see [6]. The
mass of particle collected on filter is calculated according to Equation (2):
1 1
∆m = K − (2)
0
2 2
f f
b a
where
∆m is the mass of particle collected on filter, in micrograms;
f is the frequency of the oscillating tube after particle collection, in Hertz;
b
f is the frequency of the oscillating tube before particle collection, in Hertz;
a
K is a constant (spring constant) unique to each tapered tube, in micrograms per square second.
0
The control unit calculates the mass of particles collected on the filter based on the oscillation frequency
®
1)
difference before and after sampling as given in the above equation. The 13 mm diameter Pallflex filter
used is made from glass fibres coated with plastic and is relatively insensitive to changes in humidity which
®
1) Pallflex filter is an example of a suitable product available commercially. This information is given for the convenience of users of
this Technical Report and does not constitute an endorsement by CEN of this product.
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can modify the particle mass. However, in order to minimize collection of water droplets when used in the
outdoor atmosphere the whole sensing unit is held at a temperature of 50 °C. However, this has the
disadvantage of vaporising some collected semi-volatile aerosol particles (e.g. some organic species and
ammonium nitrate) and therefore providing reliable consistent results only for those particles that are non-
volatile at and below 50 °C.
3.2.2.2 Determination of mass concentration of health-related fractions
Change in the oscillation frequency of the tapered glass tube is directly proportional to the mass of particles
deposited on the filter and is therefore independent of the physical and chemical properties of the particles.
There is no need therefore to use on-site calibration factors. With particle collection onto the filter, there is no
limitation, in principle, on the size of particles that can be detected (unlike the piezoelectric crystal). Different
health-related fractions can be sampled using particle size selective inlets, such as cyclones, impactors or
porous foam plugs. The mains-powered TEOM is widely used to monitor ambient particle levels and sampling
inlets for PM , PM and PM fractions are available.
10 2,5 1
3.2.2.3 Calibration of TEOM
Each tapered glass tube sensor has its own frequency response (K ) and so the instrument incorporating the
0
sensor is calibrated in the factory to give the required mass response. Provided that the sensor is not
damaged and the filter is fitted correctly on to the tapered glass tube, no further calibration is required.
However, as a check on the stability of the performance of the sensor, reference filters of known mass can be
used as part of a quality control audit system
3.2.2.4 Advantages and disadvantages
Table 3 gives advantages and disadvantages of TEOM instruments.
Table 3 ― Advantages/disadvantages of TEOM instruments
Advantages Disadvantages
direct measurement of dust mass detector system held at 50 °C so mass
measurement does not include liquid or
semi-volatile aerosols
no on-site calibration required mains-operated instrument, although
personal monitor available for use in
mines
response independent of chemical requires > 30 min warm up time at start
composition and particle size of monitoring.
only monitor capable of monitoring all large multi unit device not easy to move,
three aerosol fractions without calibration although personal monitor available for
factors (not at the same time) use in mines
not easy to use
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3.2.2.5 Currently available TEOM instruments
Table 4 gives an overview on currently available TEOM instruments.
Table 4 ― Currently available TEOM instruments
a
Name Portable/ Size Weight Size Flow Response Accuracy Measure-
personal selection rate time ment range
3
mm kg l/min s mg/m
Thermo static two units: can use 16,7 depends upon ± 0,75 % 0,000 1 to
TEOM any size concentration 5 000
sensor unit:
18
1400 selective − real time
360 × 280 × 330
®
series inlet for mass
control unit: inhalable, concentration
15
thoracic or averages:
430 × 380 × 220
respirable 10 min default
aerosols (10 s to
3 600 s by
choice)
R & P personal TEOM unit 2,8 uses 2,2 depends upon ± 25 % at 0,05 to 200
® 3
PDM incorporated into currently concentration 0,2 mg/m
cap lamp battery cyclone for – real time
respirable mass
243 × 87 × 193
fraction concentration
averages:
30 min default
(10 min to
60 min by
choice)
NOTE "Accuracy" is defined by the manufacturers themselves and in some cases the definitions are different.
® ®
a
Thermo TEOM 1400 series and R & P PDM are examples of suitable products available commercially. This information is given for
the convenience of users of this Technical Report and does not constitute an endorsement by CEN of these products.
®
2)
The personal version of the TEOM is available (R&P PDM ), although this was originally developed for the
mining industry and is linked to the cap lamp used by miners. It would therefore require considerable
modification to be used in general workplace environments. However, researchers are currently investigating
its use for this purpose.
3.3 Beta mass monitors
3.3.1 Operating principle
In this case, the weight of dust particles sampled on the filter (or collection substrate) is estimated by
attenuation of beta rays crossing the filter positioned between a source and a Geiger-Müller counter
(see Figure 4).
®
2) R&P PDM is an example of a suitable product available commercially. This information is given for the convenience
of users of this Technical Report and does not constitute an endorsement by CEN of this product.
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Key
1 aerosol particle collection substrate
2 Geiger-Müller counter
β beta radiation source
Figure 4 ― Schematic of beta mass monitor
Beta ray attenuation by a substance is proportional to the ratio between the atomic number and the atomic
mass of that substance. As this ratio does not vary much between the elements (apart from hydrogen), this
means that the attenuation relates to the mass of particles collected per filter unit area (see [4]). Measurement
involves recording and comparing numbers of pulses detected by the Geiger-Müller counter before and after
sampling. If N is the number of pulses per unit time for a clean filter, then:
1
N = N exp(− k × m ) (3)
1 0 β 1
and if N is the number of pulses per unit time for a particle-loaded filter:
2
N = N exp[− k()m +∆m ] (4)
2 0 β 1
where
N is the pulse count without a filter, in numbers per second;
0
k is the mass absorption coefficient, in square centimetres per milligram;
β
m is the surface mass of clean filter, in milligrams per square centimetre;
1
∆m is the surface mass of collected particles, in milligrams per square centimetre.
The pulse ratio is calculated according to Equation (5):
N
2
= exp()k ∆m (5)
β
N
1
whence the surface mass of collected particles is calculated according to Equation (6):
()ln N − ln N
2 1
∆m = (6)
k
β
Finally, the aerosol mean concentration during sampling is given by Equation (7):
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∆m× S
C =1000 (7)
Q× t
s
where
C is the aerosol mean concentration, in milligrams per cubic metre;
∆m is the surface mass of collected particles, in milligrams per square centimetre;
S is the filter effective area, in square centimetres;
Q is the sampling flow rate, in litres per minute;
t is the sampling time, in minutes.
s
Using this method, the measurement result depends on the uniformity of the deposition of the particles on the
filter and their chemical composition. It has been shown that the influence of particle chemical composition is
low for most urban pollutants (see [9]). This problem should be taken into account in the workplace where a
large variety of pollutants is encountered.
3.3.2 Determination of mass concentration of health-related fractions
Particles are normally collected on suitable filter materials and so in principle there are no particle collection or
deposition problems. However, as mentioned above, the response is affected by the uniformity of particle
deposition on the filter and so the method is normally limited to the thoracic (PM ) or respirable particle
10
fractions. Particle size selective inlets connected to the mass sensing head are used to select the thoracic or
respirable fractions.
3.3.3 Calibration of beta mass monitors
In order to determine the mass of particles deposited on the filter it is necessary to take into account the
attenuation of the beta radiation by the filter and by the particles. This is described above and in practical
direct-reading instruments is determined by alternately scanning areas of clean and mass-deposited filter.
Other complications arise from the effect associated with the geometry of the beta source and detection
system. Careful calibration against known gravimetrically assessed reference samples is therefore required.
This is initially carried out by the manufacturer and can then be routinely checked in the laboratory.
3.3.4 Advantages and disadvantages
Table 5 gives advantages and disadvantages of beta mass monitors.
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Table 5 ― Advantages/disadvantages of beta mass monitors
Advantages Disadvantages
direct measurement of dust mass includes radioactive source, which
causes problems for transportation to
and from site and for disposal
no on-site calibration required long integration periods so time
resolution poor
response independent of chemical mostly mains-operated
composition and particle size for most
common industrial aerosols
filter collection can be used for chemical naturally occurring radioactive materials
analysis may influence the result
once on-site relatively easy to use
3.3.5 Currently available beta mass monitors
Table 6 ― Currently available beta mass monitors
a
Name
...
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