Basic Air Monitoring

Basic Air Monitoring

Bureau of Workers Comp
PA Training for Health & Safety
(PATHS)

PPT-045-01 1
 Program Purpose

• Various means of detection

exist for solids, liquids and
gases.
• This program is an
overview of monitoring the
means to be used in some
safety applications or to aid
in responding to an event.

PPT-045-01 2
 Main Topics

• Hazards • Detector types

• Chemical and physical • Calibrating detectors
properties of target • Field monitoring
materials
• Sewer entry policy
• Some gas properties as an example
• Resources • Working a situation
• Propane as an example • Bibliography

PPT-045-01 3
 Hazardous Atmospheres

Residential

• CO (carbon monoxide)
• Gas leaks into buildings
• Radon
• Intruding emissions
from adjacent properties

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 Hazardous Atmospheres

Industrial
• Process areas
• Storage locations
• Gas leaks
• Flammable liquid spills
• Drums and containers
• Special activities
• Hazardous material events

PPT-045-01 5
 Municipal Operations

• Water treatment
plants
• Sewer plant
operations
• Valve pit work
• Garage work

PPT-045-01 6
Specific Field Work

• Confined space
• Trenching and shoring

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 Environmental Issues

• Clean air
determinations
• Emissions control
• Waste sites

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 Emergency Response

• Industrial rescue or
hazardous materials
response

• Emergency services

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 Hazardous Atmospheres

• Special types of
atmospheres
• Carbon monoxide
• LGP/LNG
• Radon
• Hydrogen sulfide
• Carbon dioxide
• Specialty gases
• Radiological concerns
• Other potential hazards

PPT-045-01 10
 Basic Air Monitoring

• Each of the previous situations could benefit

from air monitoring.

• Detectors are generally used to determine:

– Oxygen content
– Presence of flammable vapors or gases
– Presence of toxic materials

• Terms pertaining to characteristics of materials

for which monitoring might be used should be
discussed first.
PPT-045-01 11
 Hazard Property Terms

• IDLH: Immediately dangerous to life and

health values
• Exposure Limits: OSHA PEL: permissible
exposure limits
• TWA: Time weighted average limits expressed
in PPM which should not be exceeded during an
8-hour work shift in a 40-hour work week
• PPM: Parts per million. Can be converted into
percentage by volume by dividing the PPM
given by 10,000.

PPT-045-01 12
 Chemical & Physical Properties

• MW: Molecular weight

will help you determine if
the vapor or gas is
heavier or lighter than
air; the vapor density.

• Vapor density can be

determined by dividing
the material’s molecular
weight by 29: MW
29

PPT-045-01 13
 Vapor Density

• A comparison of a gas or vapor’s weight to air

• Air is assigned a vapor density of 1.0
• Gases or vapors with a vapor density greater than
1.0 are that many times heavier than air.
• Gases or vapors with a vapor density less than 1.0
are lighter than air.
• This will help you determine if you will monitor
high or low in an area to obtain a reading.
• May also be expressed as RGasD: relative gas
density

PPT-045-01 14
 Flashpoint Temperature

Fl.P.: Flashpoint
• The lowest temperature
at which vapors are
produced by a liquid that,
when ignited, will flash
• No continued combustion
at this temperature
• Sustained burning is at
the fire point
(temperature above the
flashpoint temperature)

PPT-045-01 15
 IP

• IP: Ionization potential

in electron volts (eV) for
a vapor or gas
• This will signify a
photoionization detector
may be used to detect
the presence of material
• Lamp rating must be at
or greater than IP of
test gas or vapor for a
precise reading

PPT-045-01 16
 Hazard Characteristics

• Before starting, fully

understand the hazards
of the material for
which you’ll monitor:

• Vapor density
• Flammable limits
• Health hazards
• Exposure limits
• Signs and symptoms of
exposure
PPT-045-01 17
 RGasD

• RGasD: Relative gas

density will indicate if
gas/vapor is heavier
or lighter than air
• If we divide the MW
by 29 (the weight of
air) this should also
approximate the
vapor density of the
gas/vapor

PPT-045-01 18
 Gas/Vapor Behavior

• Gases can stratify in air

based on their vapor
density
• Take readings from
various depths and
points in below-grade
situations
• You may need to take
readings in rooms at
different elevations and
points as well

PPT-045-01 19
 LEL/UEL

• UEL/LEL: Upper and

lower explosive limit
• Range in between is the
flammable range
• Safety Rule of Thumb
Monitor until you find 10
percent of the LEL inside
a building
• Outside: stop when you
determine 20 percent
LEL is evident

PPT-045-01 20
 UEL/LEL

• Will aid in determining the

perimeter and extent of
gas/vapor spread (100
percent of LEL, dangerous)
• Only ignition source
needed to ignite
gas/vapor
• You do not want to be
within a flammable
environment!

PPT-045-01 21
 Respirator

• NIOSH Respirator
recommendations assist
in determining the level
of needed respiratory
protection depending
upon the PPM (Mg/M3) for
a material

PPT-045-01 22
 Asphyxiation Hazards

• Simple Asphyxiants:
Displace breathable oxygen
in an area (example: carbon
dioxide)

• Chemical Asphyxiants:
Bond with red blood cells and
restrict the body’s ability to
metabolize oxygen
(examples: carbon monoxide
and hydrogen cyanide)

PPT-045-01 23
 Some Gas Particulars

IDLH IP
Gas LEL% (10%LEL) PPM % in eV
Carbon
Monoxide 12.5 1.25 1,500 .15 13.98

Hydrogen
Cyanide 5.6. 56 50 .005 13.6

Hydrogen
Sulfide 4.3 .43 300 .03 10.46

LPG 1.9 .19 19,000 1.9 10.95

PPT-045-01 24
 Carbon Monoxide

• IDLH 1200 ppm

• PEL TWA 50 ppm
• IP 14.01 eV
• RGasD .97
• LEL 12.5%
• UEL 74%

PPT-045-01 25
 LPG/LNG

• IDLH 2000 PPM (10% LEL)

• PEL 1000 PPM
• IP 10.95 eV
• RGasD 1.45 – 2.0
• LEL 2.1% (propane) 1.9% (butane)
• UEL 9.5% (propane) 8.5% (butane)
• Sa/SCBA 2000 PPM

PPT-045-01 26
 Hydrogen Sulfide

• IDLH 100 ppm

• PEL C 20 ppm*
50 ppm (10
min max
peak)
• IP 10.46 eV
• RGasD 1.19
• LEL 4.0%
• UEL 44.0%
• Sa/SCBA 100 ppm
*C=ceiling level value

PPT-045-01 27
 Carbon Dioxide

• IDLH 40,000 ppm

(4%)
• PEL TWA 5000 ppm
(.5%) 8 hours
• IP 13.77 eV
• RGasD 1.53
• LEL/UEL Non-flammable gas
• Sa/SCBA Yes

PPT-045-01 28
 Carbon Dioxide

CO2 % Max Exposure

By Volume Limit, Minutes
0.5 Indefinite
1.0 Indefinite
1.5 480
2.0 60
3.0 20
4.0 10
5.0 7
6.0 5
7.0 Less than 3 A Total Flood carbon dioxide
system will displace the
breathable oxygen and
asphyxiate those inside

Compressed Gas Assn. Handbook, 3rd Ed, page 293

PPT-045-01 29
 Other Potential Hazards

• Caution: Many materials have several hazards

associated with them.
• Some may be flammable and possess poisonous
characteristics.
• Toxic and corrosive gases may be encountered.
• Example: Hydrogen sulfide (H2S) deadens the
sense of smell and may falsely lead someone to
think it has dissipated. (LEL and UEL are 4 percent
to 44 percent, respectively - flammable and
poison)

PPT-045-01 30
 Specialty Gases

Specialty Gases
• Boron trichloride
• Diborane
• Phosphine
• Silane

Radiological Hazards
• Radon
• Industrial events

PPT-045-01 31
 Action Levels

• Assigned by policy
• When a given level is
read, personnel are
warned to take action or
to leave the area
• 29 CFR 1910.146 for
confined spaces. 10
percent LEL: permit
revocation
• Determine action levels
for gases/vapors you
may encounter
PPT-045-01 32
 Resources

• Safety Data Sheets

(SDS)

• NFPA standards
(National Fire Protection
Association)

• NFPA Fire Protection

Handbook

PPT-045-01 33
 Resources

Technical manuals:
Sax’s “Dangerous
Properties of Industrial
Materials”

Emergency guides:
“Emergency Response
Guidebook”

Each cited source has

valuable information toward
monitor planning
PPT-045-01 34
 Resources

• “NIOSH Pocket Guide to

Chemical Hazards”

• The following slides give

an overview of the
NIOSH categories to aid
in your monitoring
operations

PPT-045-01 35
 NIOSH Information Categories

• Name of material • Exposure Limits

• Formula • Measurement methods
• CAS# • Chemical and physical
• RTECS# properties
• IDLH • PPE
• Conversion: PPM to • Respirator
Mg/M3 recommendations
• Synonyms/trade
names

PPT-045-01 36
 NIOSH Categories

• Incompatibilities and
reactivities

• Exposure routes,
symptoms, target
organs

• First aid

PPT-045-01 37
 Propane as an Example

• Using Selected Categories:

– Formula: CH3CH2CH3
– CAS#: Chemical abstract service number
74-98-6
– RTECS#: Registry of toxic effects of chemical
substances TX2275000
– IDLH: 2100 PPM (10% LEL)
– Conversion: 1ppm = 1.80 mg/m3
– OSHA PEL: TWA 1000 PPM (1800 Mg/M3). 1000
PPM/10,000=0.1 percent

PPT-045-01 38
 Propane as an Example

• Physical Description
• MW (Molecular Weight): 44.1 (44.1/29=1.52
vapor density)
• Fl.P (Flashpoint): NA (Not applicable due to being
a gas)
• IP (Ionization Potential): 11.07 eV. A
photoionization detector could be used to detect
propane as long as the lamp used has an
ionization energy greater than the IP of the
material

PPT-045-01 39
 Propane

• RGasD: Relative gas density; heavier or lighter

than air
• Propane has an RGasD of 1.52 making it 1.52
times heavier than air
• Monitor low in an area
• Propane is a hydrocarbon and will “huddle” in
confined areas
• Always be thorough in your monitoring

PPT-045-01 40
 Propane

• UEL/LEL: 9.5 percent to 2.1 percent. If

monitoring to stop when 10 percent by volume
is found, 10 percent of the LEL of 2.1 percent is
.21 percent

• Respirator recommendations for propane:

(NIOSH) SA (supplied air) and/or SCBA (self-
contained breathing apparatus) at or above
2100 PPM

PPT-045-01 41
 Detectors

• General types include:

• Passive badges and dosimeters
• Tubes/pumps
• Combustible gas indicator (CGI)
• Single gas
• Multiple gas
• Flame ionization detector (FID)
• Photoionization detector (PID)
• Radiological

PPT-045-01 42
 Dosimeters

• Passive Monitors
Permeation of gases
through a membrane
onto a collection medium
• Film Badge
Desorbed with carbon
disulfide
Analyzed by gas
chromatograph

*Air Monitoring for Toxic Exposures,” Shirley A. Ness,

Van Nostrand Reinhold, 1991, page 85

PPT-045-01 43
 Tubes

• Test atmosphere is drawn

into tube
• Tubes are gas/vapor
specific
• Presence of gas/vapor
changes reagent color in
tube
• PPM and percentage
gradients on tube indicate
amount of gas/vapor in
atmosphere

PPT-045-01 44
 Tubes and Pumps

• Specific number of
pump strokes required
for precise reading if
using a manual pump

• Pump assemblies are

calibrated to draw
either 50cc or 100cc on
each stroke when set

PPT-045-01 45
 Solid State Sensors

Semiconductors can be used

for:

– General survey monitors

– Specific gases and
hydrocarbons
– Toxic gases

• Reads electrical resistance

decreases across a
Wheatstone bridge

PPT-045-01 46
 Combustible Gas Indicators

• Also called CGIs

• Catalytic combustion
• Voltage drop is read
across a Wheatstone
bridge

PPT-045-01 47
 Single Gas

• Sensor is gas-specific
• Electro-chemical principle
• Chemical specificity is due
to electrodes and
electrolytes used
• “Ticker” used by gas
companies specific to
their product
• Note sensing head

PPT-045-01 48
 Multiple Gas

• Visual and audible alarms

• Specific detector heads
may be incorporated
based on your hazards
• This one detects:

• Oxygen content
• Percent LEL
• Carbon monoxide
• Hydrogen sulfide

PPT-045-01 49
 Multiple Gas

• Read oxygen level

first to verify correct
level between 19.5
percent to 23.5
percent or reading for
LEL will be incorrect
for the challenge
gas/vapor

PPT-045-01 50
 Multiple Gas

• With pump for wand With

Pump and
attachment wand port
– May be delay in sample reading
based on length of sampling
wand/hose
– Monitor slowly so as to not
wander into hazard zone
• Without pump it will still
detect, but as a diffusion
detector

PPT-045-01 51
 Multiple Gas

• Pump brings in a
measured volume of air to
be tested With Pump:
Drawn
• More exact than hand sample is
pump more exact

• Without pump the

measurement is Without
dependent upon the Pump:
Diffusion
amount of ambient air
coming into contact with
sensing heads
PPT-045-01 52
 Flame Ionization Detector

• Also called FID

• OVA (organic vapor
analyzer)
• Carbon counter
• Current corresponds to
positive ion collection
count
• Organics ionized by a
hydrogen flame (not by a
lamp like the PID) and
counted

PPT-045-01 53
 Photoionization Detector

• Also called PIDs

• Can be hand-held or
used to monitor a fixed
location
• Reads most organic and
some inorganic
compounds
• UV (Ultraviolet) lamp
converts ionizing
materials to electric
signal (not a flame like
the FID)
PPT-045-01 54
 Radiological

• Personal dosimeters
-Self-readers
-Dosimeters

• Radiation field units

also read:
-Alpha
-Beta
-Gamma
-Neutron

PPT-045-01 55
 Radiological

• Radiation causes
ionization in the
detecting media
• Ions produced are
counted electronically
• Relationship
established between
number of ionizing
events and quantity
of radiation present

PPT-045-01 56
 Radiological

Detector Detects

Ion detection tubes Gamma and X-radiation

Proportional detection tubes Alpha
Geiger-Mueller tubes Gamma and/or Beta
Scintillation detection Alpha or Gamma

PPT-045-01 57
 Other Detection Means

• Samples are obtained by

either:
Bag sample or
Swipe sample

• Then subjected to
Gas Chromatograph
sophisticated equipment (e.g.,
gas chromatographs and
spectrophotometers)

• Each of these has its merits,

but can be time-consuming Spectrophotometer

PPT-045-01 58
 Detector Safety

• Intrinsically safe: unit won’t

contribute an ignition
source; per NEC (national
electrical code) rated for
various class, group and
division uses
• Class: type of flammable
material
• Group: types of gases or
vapors
• Division: location of the
atmosphere
PPT-045-01 59
 Detector Safety

• Explosion proof:
allows entrance of
flammable gases but
is built to contain an
explosion

PPT-045-01 60
 Calibration

• Why calibrate?
• “The calibration check is
the only way to
determine the meter is
working properly.”
• Some calibration gases:
-Methane
-Pentane
-Hexane
• Check user’s manual
Carol J. Maslansky & Steven P. Maslansky, “Air Monitoring
Instrumentation,” Van Nostrand Reinhold, 1993, page 73

PPT-045-01 61
 Calibration

• Calibrate detector on a
scheduled basis and before
use to ensure readiness
• Calibration gas can contain
various PPM of selected
gases for a single
connection and calibration
of multiple heads
• Calibration assures detector
will function within
necessary parameters for
accurate readings
PPT-045-01 62
 Calibration

• Dosimeter

• Air check on combustible

gas meter

PPT-045-01 63
 Calibration Means

• Multigas: replace detector

heads or calibrate with gas
• CGI: calibration gas
• FID: electronically zeroed
• PID: calibrated with gas of
known PPM. Adjustments
made using a span
potentiometer to fine tune
monitor; a new lamp may
also be used

PPT-045-01 64
 Match Detector to Hazard

Match the detector to the

hazard!
• In one situation, a field
team used a CGI in an
acid spill atmosphere
• Detector heads were
“poisoned” due to
contact with the acid
vapor
• Detector heads had to be
replaced and unit
overhauled
PPT-045-01 65
 Detector Heads

• Rated for the type of

hazard
• Sampling range is
also important
• Intrinsically safe for
specific atmosphere?

PPT-045-01 66
 Capabilities and Limitations

• Presence of several vapors or gases in the same

atmosphere may mask individual readings
• Time required to read a sample
• Some detectors are not meant to enter into a
flammable atmosphere; they may serve as the
ignition source
• Ensure your detector is “intrinsically safe”
• Temperature and humidity may affect readings
• Altitude may affect reading
• Obtain a monitor with the greatest versatility

PPT-045-01 67
 Minimum Response Time

• This is the time for the sample to be drawn into the

equipment and for the sensor to react to the chemical if it
is present.

• Add time to "minimum response time" if you have attached

a hose or probe extension to the inlet.

• Some units indicate that 5 to 8 seconds per foot of

attachment might be required before the sample is drawn
into the sampling chamber of the detector.

• Check manufacturer’s specifications with the unit.

OSHA Fact Sheet, DSTM 9/2005 pertaining to Confined Space Entry

PPT-045-01 68
 Conversion Factors

• Conversion factors (also referred to as relative

response): Used to correct detector readings
for gases other than calibrating gas.
• Some gases/vapors are either hot-burning or
cold-burning gases.
• This indicates how rapidly or slowly the sample
releases its heat relative to the calibration gas
in the meter’s sampling chamber.
• The calibrating gas (calibration standard)
creates a straight line on the graph relative to
its heat release.

PPT-045-01 69
 Conversion Factors

• In sampling, the heat release

of the calibrating gas will rise
in a straight line across the
graph.
• If monitoring for the gas with
which the detector was
calibrated, i.e., Methane, the
reading will need no
conversion adjustment.
Hot Burning
Gas

Cold Burning
Gas

PPT-045-01 70
 Conversion Factor

Hot-burning gases will travel more immediately up

on the graph. Their conversion factor will be less
than 1.0
Cold-burning gases travel beneath the calibration
gas on the graph. Their conversion factors will be
greater than 1.0 to adjust the reading

Hot Burning
Gas: CF <1.0

Cold Burning
Gas:
CF >1.0

PPT-045-01 71
 Conversion Factor: Example

• Example: You obtain a meter reading for a gas of

15 percent LEL - the conversion factor for the gas
is 2.5 due to it being a cold-burning gas
• To obtain a true reading: 2.5 x 15 percent=37.5
percent
• This is a dangerous atmosphere that you may wish
to vacate immediately
• You could be entering a highly flammable area

PPT-045-01 72
 Reading

• Knowing the correction

factor, determine the
meter reading
• Example: your true
meter reading should not True Reading
(80 PPM)
exceed 80 PPM; the gas’s
correction factor is .8 Meter
Reading X
Correction
Factor
(100 PPM) (.8)
• True meter reading of 80
PPM divided by CF of .8
= Monitor until meter
reads 100 PPM

PPT-045-01 73
 Reading

• Another example:
The exposure limit for a gas
should not exceed 125 PPM
The correction factor for the True Meter Reading
gas reading is .9 (125 PPM)

So, monitor until your meter Meter Correction

Reading X Factor
reads 138 PPM (138 PPM) (.9)

(Divide true meter reading

by correction factor to get
meter reading at which to
stop)

PPT-045-01 74
 Field Monitoring

• Determine zones
• Hot, warm, cold zones
• Downwind hazard areas
• Conduct hazard & risk
assessment

PPT-045-01 75
Hazard and Risk Assessment

• Know the hazard characteristics

• Match the correct detector to the hazard
• Understand the detectable ranges
• Will conversion factors apply to the target
hazard?
• Will temperature or humidity affect readings?
• Is monitor intrinsically safe? Can it be calibrated?
• Are capabilities and limitations understood?
• What other safety concerns also apply?
-PPE -Fire protection -Backup
-Ventilation -Lock-out/tag-out

PPT-045-01 76
 Field Monitoring

• Perform tasks to make

area safe for monitoring
• Map the release area
• Select a pattern to use in
the search area
• Brief the monitoring team

PPT-045-01 77
 Field Monitoring

• Monitor the suspect

location for initial
readings
• Continue to monitor
throughout an event
since conditions can
change due to the
possible intrusion of
gases or vapors
• When LEL or PPM
readings are exceeded,
vacate the location

PPT-045-01 78
 Detector Selection

• Always match the

detector to the hazard
• Obtain user information
from the manufacturer
• Determine full capabilities
of monitor
• Lack of preparation may
put you into an
analogous situation

PPT-045-01 79
 Detector Selection

• Never attempt to use

the equipment until
fully and properly
trained
• Understand the
function of each
setting
• Run simulated
incidents with your
staff

PPT-045-01 80
 Detector Selection

• Ensure your staff is

confident in the use

• Have all questions

answered completely
by the vendor during
the turn-over briefing
and staff training.

• “Know before you go”

PPT-045-01 81
 Detector Selection

• Maintain equipment in
accordance with
manufacturer’s
recommendations

• If in doubt regarding
maintenance and
calibration, consider
contracting with the
vendor to perform these
services

PPT-045-01 82
 Detection Sequence

• Monitor first for oxygen

content since oxygen
depletion or enrichment
will result in an incorrect
reading in other
categories

• Then monitor for the LEL

• Then for levels of other

materials for which the
detector is calibrated
PPT-045-01 83
 Sewer Entry

• Per 29 CFR 1910.146 Appendix E

• Entrants should be equipped with atmospheric
monitoring which sounds an audible alarm, in
addition to its visual readout, when:

– Oxygen concentration is less than 19.5 percent,

– Flammable gas or vapor is at 10 percent or more of the
lower flammable limit (LFL); or
– Hydrogen sulfide or carbon monoxide is at or above 10 PPM
or 35 PPM, respectively, measured as an 8-hour time-
weighted average

PPT-045-01 84
 Sewer Entry

• The oxygen
sensor/broad-range
sensor best suited for
initial use in situations
where actual or potential
contaminants have not
been identified
• Substance-specific
instruments may then be
used when hazard is
identified

PPT-045-01 85
 Work a Situation

• Working with one of

your in-house SDSs
• Select an in-house gas
or flammable liquid
• Identify hazard
characteristics
• Select a monitor
• Plan your response
• Create your in-house
policy and procedure

PPT-045-01 86
 Remember

• These instruments are not toys

• They are very capable within the realm for
which they were designed
• They also have limitations
• When in doubt - check with the detector
manufacturers or vendors
• Do not take their use for granted. The lives
of your staff may be in the balance.

PPT-045-01 87
 Bibliography

• Shirley A. Ness, “Air Monitoring for Toxic

Exposures,” Van Nostrand Reinhold, 1991
• Carol J. Maslansky & Steven P. Maslansky, “Air
Monitoring Instrumentation,” Van Nostrand
Reinhold, 1993
• “Handbook of Compressed Gases,” Compressed Gas
Association, Inc., 3rd Edition, 1990
• “NIOSH Pocket Guide to Chemical Hazards,”
Department of Health and Human Services, CDC,
NIOSH Publication No. 2005-149, 2005
• OSHA Fact Sheet, DSTM 9/2005

PPT-045-01 88
Questions

PPT-045-01 89