Air Sampling 

Introduction

10/25/2010
Purpose of Air Sampling

1. Evaluate exposures to the public and worke2. Document measures used to control airborn

concentrations.

3. Warn workers of unexpected releases.4. Assist in materials balancing.5. As part of a respiratory protection program.6. Satisfy regulatory and/or license requiremen7. Obtain data for use in potential litigation.
General 

Terminology
The radioactive material being collected may be pre

one of two forms.1. Particulates (could be collected on a filter)2 Gases and vapors (would not be collected o

Form of Airborne Radioactive Material

. Gases and vapors (would not be collected o
Particulates

A collective term describing airborne solids and liqudroplets. There are several ways to categorize paa) Aerosol. This term is used in various ways, usually as a 

for airborne particulate. Occasionally it only refers to par

Form of Airborne Radioactive Material

that are in a stable or quasi-stable suspension in air. 

b) Dusts. Particulates produced by the disintegration of ma

during mechanical processes such as grinding. Dusts alarger than one micron (um) in size.

c) Fumes. Particulates produced by chemical reactions, e

oxidation. They may condense from the gaseous state avolatilization of melted substances. The typical size ranfumes would be 0.1 - 1.0 um. 
Particulates

d) Smoke. Small particulates (ca. 0.5 um) resulting from th

incomplete combustion.

e) Mists and Fogs. Liquid droplets produced by condensat

5 - 40 um range the particulates are referred to as fog. P

b 40 i di t f d t i t

Form of Airborne Radioactive Material

above 40 um in diameter are referred to as mists.
Gases and Vapors

Gases can be defined as materials that under normconditions exist in the gaseous phase.Vapors are the gaseous phase of substances typicexisting as a liquid or solid at room temperatureForm of Airborne Radioactive Materialexisting as a liquid or solid at room temperature.
Sampling 

“Air sampling” generally means a sample is collectfinite period of time and sent to the laboratory for aA grab sample is collected in a short period of time 10 minutes) at a specific location It is not used to dSampling vs. Monitoring10 minutes) at a specific location. It is not used to d

an average concentration. Instead, it is usually collsee if anything is there. In some cases repetitive gsamples might be used to evaluate temporal fluctuof some sort.
Monitoring 

“Monitoring” usually indicates a “real time” analysis performed. In the DOE literature however, the ter“monitoring” has no specific meaning. Air sampling systems that perform a real time analSampling vs. MonitoringAir sampling systems that perform a real-time anal

airborne radioactive material are generally referred continuous air monitors (CAMs). Their primary puralert workers to unexpected releases rather than to accurate measurements of the concentration. Mosinvolve a “sampling” system of some sort.
The concentration of airborne radioactive material 

determined:

1. For a specific radionuclide (e.g., I-131), o2. As a gross alpha or beta concentration 

Nuclide-Specific vs. Gross Activity MeasAlthough gross beta and alpha measurements are common, nuclide-specific (isotopic) analyses are pWhen gross alpha or gross beta measurements arperformed, some method must be employed to corthe contributions from the naturally occurring radon thoron decay products.
In some cases, the goal is to collect a representativ

sample, i.e., a sample whose characteristics are idthe atmosphere being analyzed. In most cases, this is accomplished if the concentrthe sampled air reflects the average ambient conceRepresentative Sample
There are two general categories of radionuclides 

sufficiently difficult to collect and analyze, that we omake no attempt to do so:

• Noble gases (e.g., at nuclear power plants)

Very short lived nuclides (e g at accelerators

Difficult Radionuclides to Assess

• Very short

-lived nuclides (e.g., at accelerators

One approach to “assess” such nuclides is to meaambient levels of gamma and/or beta radiation with detectors (e.g.., GMs) or passive dosimeters (e.g., In general, these methods cannot distinguish the dresponse to the radionuclides of interest from its reto background.
Characteristics of Airborne 

Radioactive Material that Aff

Dose
Three characteristics of the airborne radioactive m

affect the dose due to inhalation:

1. Concentration2. Particle size

Characteristics that Affect Dose

3. Clearance class
1. Concentration

The focus of air sampling is usually to quantify the concentration of the airborne radioactivity, e.g., uCpCi/m3, Bq/m3. In some cases we simply want to determine if therCharacteristics that Affect DoseIn some cases, we simply want to determine if ther

been an increase in the concentration rather than tquantify it.
2. Particle Size

The dose depends on particle size because the sizdetermines the region of the respiratory system thaparticles are deposited in.The size of radioactive particulates is usually expreCharacteristics that Affect DoseThe size of radioactive particulates is usually expre

their activity median aerodynamic diameter (AMADAMAD describes the aerodynamic behavior of the particulates rather than their physical size. The terthermodynamic diameter (AMTD) rather than aerodiameter (AMAD) is sometimes used to describe sparticles whose deposition is due to diffusion ratheimpaction or gravitational settling.
2. Particle Size

For regulatory purposes in the U.S., the usual assuthat airborne particulates have an AMAD of 1 um.The current ICRP recommendation is that a 5 um sassumed for particulates in the workplace and that Characteristics that Affect Doseassumed for particulates in the workplace and that 

assumed for the environment (public exposures). In the workplace, 5 um is probably a more realistic than 1 um.
2. Particle Size

The AMAD does not describe a physical size of the particles, it describes their aerodynamic behavior. Furthermore, it only describes the radioactive partiCharacteristics that Affect Dose

AMAD means “Activity Median Aerodynamic Diam

1 um

1 um particles

unit density 
3. Clearance Class

Different chemical compounds are cleared from the different rates. The rate at which they are cleared described in terms of a half time. On the basis of a compound's half time in the pulmonary region, ICRassigns it to one of three clearance classes:Characteristics that Affect Doseassigns it to one of three clearance classes:

Class D materials (half time less than 10 days) 

essentially equivalent to ICRP 60 class F

Class W materials (half time of 10 - 100 days) 

essentially equivalent to ICRP 60 class M

Class Y materials (half time longer than 100 da

essentially equivalent to ICRP 60 class S 
3. Clearance Class

This classification is based on chemistry and is indof the radionuclides half-life. A radionuclide with a half life can still be placed in clearance class Y.In general, the longer the clearance half time the gCharacteristics that Affect DoseIn general, the longer the clearance half time the g

dose and the lower the ALI.Listings of the ALIs (e.g., 20 CFR 20, Federal Guid

Report 11) identify which radionuclides and compoassigned to the various clearance classes. If the chform of the radioactive material is not known, the mrestrictive class is assumed.
3. Clearance Class

Characteristics that Affect Dose
Where We Perform Air 

Sampling

9/24/2009
There are three locations where air sampling is pe

1. Workplace2. Stack (effluents) 

Where We Perform Air Sampling

3. Environment.
Workplace

Fixed air samplers (FAS) are used if the concentraarea frequently has the potential to become excessnear glove boxesPortable samplers are used to obtain short term saWhere We Perform Air SamplingPortable samplers are used to obtain short-term sa

areas that don't require continuous sampling, e.g., where radioactive material is occasionally handledGeneral air (GA) samples estimate the average concentration in the room. Sampling near the room exhaust grill is a good way to obtain a representatisample to calculate the average room concentratio
Workplace

Breathing zone (BZ) samples are collected to deteconcentration in the air inhaled by the worker. This higher than the room average concentration becauworker is typically close to the source of airborne contamination. Where We Perform Air SamplingBZ samplers, might have the filter holder attached collar with the pump and flow meter attached to the Such devices are referred to as personal air monitoor lapel air samplers. 
Workplace

Unfortunately, the sampling flow rates of these typesamplers might be so low that there is no measuracollected activity. Due to a lack of worker acceptance, they are rarely Where We Perform Air Sampling

p ,y y

continuously. Sometimes, a fixed air sampler is used to estimate concentration in the “breathing zone.” When this is sampling head is usually located in front of, and justhe worker’s head. 
Workplace

Continuous air monitors (CAMs) are real-time monwarn the worker to leave the area in the event of aunexpected release. They are not used to calculataverage concentrations. Where We Perform Air SamplingFalse alarms caused by airborne radon decay prodcommon problem with CAMs. Improper placement of a CAM might cause accidereleases of airborne contaminants to go undetecteespecially true with short-term “puff” releases (e.g.opposed to gradual releases caused by a leak).
Workplace

Where We Perform Air Sampling

Portable Air Sampler

Continuous Air Monitor (CAM)
Stack/Effluent

Stack sampling is usually (but not always) continuothe samples analyzed on a daily or weekly basis. One problem is ensuring that a representative samparticulates is collected on the filter. This can be d

f ff

Where We Perform Air Samplingbecause of the highly dynamic flow of air in stacks 

affects the distribution of particulates in the effluenThe methodology employed for stack sampling is gthat described in Appendix A of ANSI N13.1 (1969)some cases, it is necessary to employ the methodothe latest version of ANSI N13.1 (1999).
Stack/Effluent - ANSI N13.1 (1969)

Describes how to sample stacks. Requires “isokinetic sampling” be performed for particulates. In isokinetic sampling, the velocity of air/gas entering the nozzle is the same as it is at thWhere We Perform Air Samplingair/gas entering the nozzle is the same as it is at th

in the stack in the absence of sampling equipmentIn subisokinetic sampling the velocity entering the lower than isokinetic. The theory is that we would overestimate the activity associated with the particespecially the large particulates.
Stack/Effluent - ANSI N13.1 (1969)

In superisokinetic sampling the velocity entering this faster than isokinetic. The theory is that we woulunderestimate the activity associated with the partiespecially the large particulates.Where We Perform Air SamplingThe standard also recommends sampling probe be with multiple withdrawal points.
Stack/Effluent - ANSI N13.1 (1999)

Sets performance criteria, does not describes how sample. Does not require “isokinetic” sampling.R d b ith i l i t t tiWhere We Perform Air SamplingRecommen

ds pro

bes with single poin

t ex

traction.

Requires flat air velocity profile at sampling point.Requires tracer studies with gases and 10 um partdemonstrate complete mixing at sampling point.Expensive to implement.
Stack/Effluent

Where We Perform Air Sampling

Multi-point withdrawal

“rake”

ANSI N13.1 1969

Single-point withd

“shrouded pro

ANSI N13.1 1

Images courtesy of Hi-Q
Environment

Airborne concentrations in the environment are lowrequires long sampling times at high flow rates. Thmost common approaches:

1. Gross alpha and/or beta analysis after samp

) f f 

Where We Perform Air Sampling

vol) for one week at 1 - 2 cfm through a 47 m

2. Nuclide specific analysis after sampling for o

week at 40 cfm (high vol) through an 8 x 10 

Problems can include the collection of large quantidust and other non-radioactive particulates, selectiappropriate sampling locations and maintaining eqat remote sites.
Environment – low vol sampler

Where We Perform Air SamplingShelter for sampler known as a “dog house” 
Environment – high vol sampler

Where We Perform Air Sampling

Solar powered systems are available.Images courtesy of Hi-Q
How We Perform Air Sampli

- Equipment

9/24/2009
Equipment Overview

A basic sampling system consists of an:

Air filter - to collect particulatesFlow meter - to determine sampling flow rate o

How We Perform Air Sampling - Equipme

pg 

Elapsed timer - to determine sampling duration Pump – to move the air through the sampler 

If it is necessary to collect gases or vapors, additiocomponents are required, e.g., adsorber cartridge 

bubbler.
How We Perform Air Sampling - Equipme

Air Flow

Adsorber cartridge 

(e.g., charcoal)

Air Filter

Sampling

Head

1.5 CFM

Flow Meter

Pump

Timer

10080.0 min
Filters - General

A filter is the most common device employed to coparticulates. Occasionally, a device known as an impactor is usinstead.How We Perform Air Sampling - EquipmeThe three major types of filters are: Membrane

Glass fiberCellulose
Filters - Membrane Filter

• surface loading filter primarily used with alph

emitters

• typical pore sizes: 3 or 5 um• high collection efficiency not affected by flow • easily digested

How We Perform Air Sampling - Equipme

easily digested

• goes transparent in LSC cocktail• accumulation of dust results in increased re

to air flow 

• fragile
Filters - Glass Fiber Filter

• the collection (up) side is irregular and wavy• an accumulation of dust has minimal effect on 

filter’s resistance to air flow. This makes it usef

dusty atmospheres and it is often used for 

environmental sampling

How We Perform Air Sampling - Equipme

environmental sampling

• for most types of glass fiber filters, their collect

efficiency is not affected by flow rate

• burial losses of alpha particles and low energy 

particles is minimal

• more rugged than membrane filters but still so

fragile

• very hard to digest for radiochemical analysis
Filters - Cellulose Filter

• Whatman 41 is the most common cellulose filte

sampling radioactive particulates although Whamight be a superior choice. 

• rugged

• easily digested for radiochemical analysis

How We Perform Air Sampling - Equipme

easily digested for radiochemical analysis

• particulates collected throughout depth of filter 

losses of alpha particles and low energy beta paare significant (e.g., 50%)

• accumulation of dust on the filter results in incre

resistance to air flow

• collection efficiency is affected by flow rate - th

face velocity should exceed 90 cm/s or so
How We Perform Air Sampling - Equipme

Open Face 

Sampling Head In-line S

Open face 

sampling head 

with filter and 

charcoal 

cartridge

Images courtesy of Hi-Q
How We Perform Air Sampling - Equipme

Cassette for 8” x 10” air filters used in high volumsampling 

Image courtesy of Hi-Q
Collecting Gases/Vapors

The primary methods used to collect gases and va

• Adsorption•

Absor

ption

How We Perform Air Sampling - Equipme

• Condensation
Collecting Gases/Vapors - Adsorbers

Adsorbers are solid granules with large surface areare packed in cartridges or tube. Examples: Indicating silica gel for tritiated water How We Perform Air Sampling - Equipme

Molecular sieve for tritiated water vapActivated charcoal for iodineSilver zeolite for iodine
Collecting Gases/Vapors - Adsorbers

Typical adsorber cartridges – note arrow indicating directionHow We Perform Air Sampling - Equipme
Collecting Gases/Vapors - Absorbers

Absorbers are liquids that preferentially dissolve thgas/vapor of interest when the sampled airstream through the solution. The “containers” used to hold absorbing solutions are known as bubblers and imHow We Perform Air Sampling - EquipmeExamples of absorbing solutions:

Distilled water for tritiated water vapor (HTOEthylene glycol for tritiated water vapor (HTHydrogen peroxide for sulfur dioxide (e.g., SSodium hydroxide for carbon dioxide (e.g., C

Analysis usually involves counting one ml of the soLSC. 
Collecting Gases/Vapors - Absorbers

How We Perform Air Sampling - Equipme

To pump

Air inbubbler solution
Flow Meter - General

The flow meter measures the volumetric flow rate osampler (e.g., cfm, lpm, ml/min), and/or the total vothe sample (e.g., cubic feet, liters, mls, m3).

The most commonly employed flow rate meters ar

How We Perform Air Sampling - Equipme

y py

rotameter and a very similar device, the by-pass roAnother method to determine the flow rate is to mepressure drop across a constriction in the sample lventuri or orifice meter).
Flow Meter - Rotameters

How We Perform Air Sampling - Equipme

Standard rotameter By-pass rotam

Image courtesy of 
Flow Meter - Total Volume Meter

The most commonly employed total volume meter gas meter, sometimes used in combination with a fmeter. At some facilities, a total volume meter is used to mHow We Perform Air Sampling - Equipmethe flow rate at the beginning and end of samplingdone by measuring the time it takes for a given volair to be sampled. To calculate the flow rate (e.g., 2the volume of air (e.g., 5 cubic feet) is divided by thtook to collect that volume (e.g., 2 minutes). 
Flow Meter - Mass Flow Meter

The mass flow meter is an electronic device that caused to simultaneously measure flow rate and the volume of air that has been sampled.The mass flow meter has the advanta

ge that its me

How We Perform Air Sampling - Equipmethe flow rate and volume at standard temperature apressure (e.g., scfm, slpm, etc.) conditions. 
Flow Meter – Calibration

Flow meters must be calibrated at least once per yafter any maintenance or adjustment that might affflow meter response. This involves relating the instread out (e.g., cfm, lpm, inches of water) to the actrateHow We Perform Air Sampling - Equipme

.

Images courtesy of Hi-Q
Elapsed Timer

Air sampling systems used for short periods (e.g.., minutes) might not employ an elapsed timer - the time might be measured a watch. Systems operatunattended for long periods require an elapsed timHow We Perform Air Sampling - EquipmeDiscrepancies in the clock time and the elapsed timshould be explained. The DOE Environmental RegGuide for Radiological Effluent Monitoring and Environmental Surveillance (DOE 0173T) indicates elapsed timer is not required if a total volume meteemployed.
Elapsed Timer

The elapsed timer might be resettable or non-resetand mechanical or electronic. With a resettable timreading is set back to zero at the beginning of each sampling period. This reduces the chance that the be misread and eliminates the need for a mathemaHow We Perform Air Sampling - Equipmecalculation (subtraction). Unfortunately, the time inby a resettable timer can be erased accidentally. Almost all new timers are electronic. In general, themore prone to failure than the older mechanical deespecially in extreme temperatures.
Elapsed Timer

Periodic accuracy checks need to be performed on timers. Regulatory Guide 8.25 recommends that therror be under 1% (approximately 14 minutes/24 hDOE recommends that the timer reading be correctwo minutes/24 hours. For such calibrations, the siHow We Perform Air Sampling - Equipme

, 

from the NIST atomic clock in Colorado could be eIt is useful to have some means of alerting people sampling system has shut down. This might be donwarning light or a more elaborate system whereby is sent to some monitoring location or cell phone n
Pump

There are two major categories of “pump”:

Positive Displacement Pump (low volume saCentrifugal Blower/Fan (high volume sample

How We Perform Air Sampling - Equipme

g (g p 

To maintain a constant flow rate during the sampliperiod, many air sampling systems incorporate an controller.
Positive Displacement Pump

For low volume (Low Vol) sampling e.g., < 2 cfmContinuous sampling (e.g., in workplace, environmstacks) and sometimes short term sampling. How We Perform Air Sampling - EquipmePositive displacement pumps require little maintencan move air against significant resistance.Common types: rotary vane pump (self-lubrica

rotary vane pump (oil-lubricatediaphragm pumppiston pumprotary lobe pump 
Centrifugal Fan/Blower

For high volume (hi vol) sampling e.g., > 5 cfmCentrifugal fans are used for hi vol continuous sam(e.g., the environment) and short term sampling (eworkplace, emergency response). How We Perform Air Sampling - Equipme

p , gyp )

Centrifugal fans that use electrical contacts called require considerable maintenance if they are run continuously. Brushless hi vol systems, although more expensivealmost maintenance-free and are generally preferr
How We Perform Air Sampling - Equipme

Self-lubricating (carbon vane) rotary vane pump with flow controller

Centrifugal fan/blowwith brushes
How We Perform Air Sampling - Equipme

Side view showing brushes on opposite sides of commutator

Worn brush in need of replacement
Class Exercise

A radionuclide might be present in the air as both a a particulate.Nevertheless, in the following table indicate the moform of the specified radionuclides and identify one How We Perform Air Sampling - Equipme

p y

collection devices that would be suitable.
Nuclide Gas/Vapor Particulate Possible Collection 

H-3

C-14

P-32S-35

Co-60

Kr

-85

Sr-90Tc-99

I-131

Xe-133

U-238

Pu-239 
Appendix

ICRP 30 and 66 Models of the ICRP 30 and 66 Models of the

Respiratory System

9/24/2009
ICRP 30 Respiratory System

Regions of the Respiratory SystemThe ICRP 30 model, still the basis for most regulatithe U.S. divides the respiratory system into three pa

Nasopharynx (N-P)

Tracheobronchial Tree (T-P)Pulmonary Region (P)
Naso Pharynx (NP)

Region

Tracheo Bronchial 

T (TB)

Pulmon

Reg

Tree (TB)

Regions of the Respiratory System
ICRP 30 Respiratory System

Inspirable Mass Fraction Fraction of the aerosols that are inspirable. Inspirabparticles can be inhaled and therefore can reach thnasopharynx. Their 50% cut point is 30-40 um. Thoracic Mass Fraction Fraction of the particulates that penetrate into the thregion (tracheo-bronchial tree). Their 50% cut point Respirable Mass FractionFraction of the particulates that penetrate into the pregion. Their 50% cut point is typically 2.5 - 5 um.
ICRP 30 Respiratory System

Respirable ParticlesThe definition of respirable particles varies consideSometimes it refers to particles less than 10 um, i.ethat can get into the tracheo-bronchial tree.The more “official” definitions define respirable partthose that can get into the pulmonary region/alveolmost common “official” 50% cut point is 3.5 – 4 umit might be as low as 2.5 or as high as 7 um.
ICRP 30 Respiratory System

Particle Deposition Inhaled particulates are not necessarily deposited - may be exhaled. Those that are deposited can be The clearance mechanisms for particles deposited pulmonary and tracheobronchial tree regions differ pulmonary and tracheobronchial tree regions differ. 

such, the hazards associated with particles depositthese regions differ. Dichotomous samplers collect the respirable and thmass fractions separately.
Particle Deposition 

This graph gives an idea as to how different particle sizes will be deposited. The lowest percent deposition in the respiratory systemICRP 30 Respiratory Systemthe respiratory system

occurs for 0.3 um particles.Nasopharynx (N-P)Tracheobronchial Tree (T-P)Pulmonary Region (P)
ICRP 66 Respiratory System

The ICRP 66 lung model, officially known as the hurespiratory tract model (HRTM), is sufficiently compdose calculations require the use of computer codeRegions of the Respiratory SystemThe respiratory system is divided into the:

1. Extrathoracic (ET) airways of the head and n2. Thoracic airways, i.e., the lungs

Lymph nodes are associated with both the extratho(LNET) and thoracic components (LNTH

)
ICRP 66 Respiratory System

Regions of the Respiratory System1. Extrathoracic (ET) airways of the head and neck

ET1 anterior nasal passage (front of nose)

ET

2 posterior nasal and oral passages (ph

larynx)

2. Thoracic airways, i.e., the lungs

BB bronchial passages (trachea, generatbb bronchiolar (generations 9 - 15) Al alveolar (gas exchange region).
ICR

Resp

Sy
ICRP 66 Respiratory System

Regional Deposition of Inhaled Particulates in RWorkersThe default particle size for the workplace is 5 um.

Region % Deposition for 5 um Particles

ET1 33 85

33.85

ET2 39.91

BB 1.78

bb 1.10

Al 5.32

Total 81.96
ICRP 66 Respiratory System

Regional Deposition of Inhaled Particulates in Mof the PublicThe default particle size for the general public is 1 uDifferent reference values are employed for the follages: 3 months, 1 year, 5 years, 10 years, and adu

Region % Deposition for 1 um Particles

3 month 1 y 5 y 10 y 15 y Mal

ET1 20.97 21.07 17.39 17.75 13.91 

ET2 27.20 27.30 22.32 22.86 18.13 

BB 1.04 1.04 1.03 1.17 1.69 

bb 2.05 1.71 1.85 1.70 2.00 

Al 8.56 9.64 9.85 9.51 10.65 

Total 59.82 60.76 52.44 52.99 46.38 
ICRP 66 Respiratory System

ClearanceClearance of deposited material occurs by two proc

• Particle transport to the GI tract and lymph nod

same for all materials).

• Absorption into the blood. This depends on the 

form of the material. Absorption rates are clas

Fast (F)Moderate (M) Slow (S)

F, M and S are essentially equivalent to the ID, W, and Y classifications. 
ICRP 66 Respiratory System

Dosimetry – target cellsThe target cells for cancer induction and dosimetry

Extrathoracic airways (ET): basal cells of the epBronchial passages (BB): basal cells and secretBronchial passages (BB): basal cells and secretBronchiolar region (bb): secretory cells
ICRP 66 Respiratory System

Dosimetry – tissue weighting factors 1. Extrathoracic (ET) airways of head and neck (w

T 

Extrathoracic airways are treated as a “remaindeThe assigned fraction of w

T attributed to ET1 is 0

assigned fraction attributed tp ET assigned fraction attributed tp ET

2 is 0 998 is

0.998.

2. Thoracic airways, i.e., the lungs (w

T = 0.12)

The assigned fractions of w

T attributed to the bro

region (BB), the bronchiolar region (bb) and the ainterstitial (Al) regions are 0.333, 0.333 and 0.33