Gas/Vapor/Particulate Sampling, Calibration, Detector Tubes,
CGM, PID, and Breathalyzer
Lab Exercise Elements:
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Prepare a series of standards
Calibrate air sampling and measurement devices
Measure and record the concentrations using:
o Detector Tubes
o Photo Ionization Detector (PID)
o Combustible Gas Meter (CGM)
o Breathalyzer
Complete the tables
Plot the data
Answer the questions
Equipment:
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10-Liter Tedlar gas bags
Microliter syringes
One rotameter
Air sample pump calibrated to a known flow rate
Solvent stock solution
Colorimetric indicator tubes (Gastec Sensidyne)
Detector Tube samplepump (GastecSensidyne, piston-type)
Photo Ionization Detector
Combustible Gas Meter
Breathalyzer
Calibration of Colorimetric Tube Hand Pumps using a Bubble Soap Meter:
Materials needed are a 100 ml burette, Tygon tubing, a soap reservoir with water, a mechanism to secure the
burette and a detector tube pump (Sensidyne).
Leak Check for Detector Tube Pump:
Perform a leak check.
1. Insert an unopened tube into the bung.
2. Pull the piston pump and watch for expansion of volume over several minutes. If a leak is detected,
disassemble pump front plate and remove exhaust valve disc. Wash disc in warm, soapy water, rinse, dry and
re-assemble. Repeat leak check. If leak still occurs, replace valve disc with a new one.
Calibration of Stroke Volume for Detector Tube Pump:
1. A soap bubble is started by inverting the burette into the soap container. (This may be facilitated by rinsing the
burette with soapy water first to lubricate the inside column walls.)
2. Attach a hand pump to the colorimetric tube at the end of the Tygon tubing connected to the burette.
3. Draw the bubble up the column to the first reference mark.
4. Draw the air sample, one pump stroke.
5. Allow piston to expand fully to the end of the stroke. Bubble will move up column and stop. This is the
volume of air that the pump draws per stroke (called the stroke volume).
6. Repeat steps 3 through 5, three times and determine an average stroke volume. It should be 100 ± 5ml.
7. Once a stroke volume of 100 ml has been verified, airborne measurements can begin.
Gas/Vapor/Particulate Sampling, Calibration, Detector Tubes,
CGM, PID, and Breathalyzer
Lab Exercise:
1.
2.
3.
4.
5.
Remove the air out of a clean 10 Liter gas bag using the lab bench top vacuum connection.
Fill the gas bag with 10 Liters of air using lab air passing through a rotameter. For example, if the lab air
passing though the rotameter has been determined to be 2 LPM, use the stop watch to record the time required
to fill the bag and stop flow to the bag after 5 minutes (i.e. total 10 Liter volume).
For a single solvent, prepare two standards in the concentration range of interest (0 ppm, 50 ppm, 500 ppm,
1000 ppm and 5000 ppm are suggested) by injecting the calculated amount of liquid solvent into the filled 10
Liter gas bag through the bag septum. Record the actual calculated concentration (column 1 of Table 2) given
the amount of solvent actually injected (Column 2 of Table 2).
Following the directions for use of the detector tubes, CGM, PID and Breathalyzer, take 2-3 replicate sample
readings, record the readings and the average values in Table 2, in the appropriate data columns.
Plot the readings versus the concentration for the detector tubes, CGM and PID for the chemicals tested.
For the chemicals shown in Table 1, record the molecular weight (MW), liquid density (Density), ionization
potential (IP), vapor pressure (VP), Lower Explosive Limit (LEL), Permissible Exposure Limit (PEL),
Threshold Limit Value (TLV) and Immediately Dangerous to Life and Health (IDLH) values. Refer to the
latest editions of the NIOSH Pocket Guide and the TLV Booklet or literature.
Table 1. Physical and Chemical Characteristics of Common Solvents.
Solvent
MW
Density
IP (eV)
VP(mm Hg)
LEL (%)
PEL(ppm)
TLV(ppm)
IDLH(ppm)
Acetone
Benzene
Ethanol
Toluene
Table 2. Gas Standard Preparation & Direct-Reading Measurements for Ethanol.
Gas Standard
(ppm)
0 ppm
250 ppm
1000 ppm
(L)
Detector Tube
Readings
3 Replicates and
Mean
CGM Readings
PID Readings
3 Replicates and
Mean
3 Replicates and
Mean
Breathalyzer
Readings
3 Replicates and
Mean
Gas/Vapor/Particulate Sampling, Calibration, Detector Tubes,
CGM, PID, and Breathalyzer
BW Gas Alert Micro 5 Gas Detector with PID
Background: The Gas Alert Micro5 can simultaneously detect up to five atmospheric hazards including oxygen,
percent LEL combustible gas,Hydrogen Sulfide, Carbon Monoxide and photoionization detector (PID) with
correction factors for a number of Volatile Organic Compounds (VOCs). The PID uses ultraviolet light as a
source of energy to remove an electron from neutrally charged molecules creating ions and an electrical current.
The ionization energy, measured in eV, is the amount of energy needed to remove an electron from a specific
molecule. The PID can only detect substances with ionization energies lower than the lamp’s output of 10.6 eV.
1.
2.
3.
4.
5.
6.
7.
Press
to turn on the unit. Watch as the unit cycles through the start-up routine:
a. Battery Check
b. Date/Time
c. Datalogging
d. Self-Test of Sensor and Power
e. LEL and PID correction factors
When the detector reaches the “Pump Test”, watch for the “Block inlet” notification and place your finger
over the inlet and wait for “Pump Test Successful” message.
Important Note: The O2 sensor test requires an ambient atmosphere of 20.9% O2at each start-up in order
accurately calibrate before use.
The final test shows the days before next calibration.
The pump will now display ambient readings in ppm for H 2S, CO, and the
PID (shown here as SO2), as well as % O2, and % LEL
Pressing the
and
simulateously accesses the options menu from which alarm, span
gas parameters, PID and %LEL correction factors, display, datalogging, time/date, and
other selections can be made.
Calibration can be done by pressing
and
simultaneously in a clean atmosphere.
a. The unit will first auto zero the toxic gas sensors and calibrate the O 2 sensor automatically.
b. Next it will enter “auto span mode.” The toxic gases can then be calibrated simultanously or one
at a time depending on the type of span gas available. The correct span gas values must be set in
the Options menu before beginning calibration.
c. Attach span gas to the pump inlet and turn on regulator to begin calibration.
d. Wait for completion of calibration (2 minutes), the meter will then prompt for the next span gas.
e. If you choose not to span the other sensors, press
to continue with the calibration process.
f. Press
to choose to set calibration dates on the sensors that were calibrated during this session
or press
to skip this step.
g. TWA and STEL alarms can be chosen by pressing
and following screen prompts or
may
be pressed to skip this step.
h. Finally press
to save calibration information.
To turn off the unit press and hold
and wait for the countdown to complete.
Gas/Vapor/Particulate Sampling, Calibration, Detector Tubes,
CGM, PID, and Breathalyzer
TSI SidePak Personal Aerosol Monitor Model AM510
Background:An aerosol particle counter works on the principal of either light scattering or light blocking. An
aerosol stream is drawn through a chamber with a light source (either Laser Based Light or White Light). When a
particle is illuminated by this light beam, it is redirected or absorbed. Light scattered by a single particle in a
specific direction in relation to the original direction has a unique signature which relates to the size of the particle.
This allows for sizing and counting of individual particles. The SidePak Personal Aerosol Monitor is a miniature
battery operated laser photometer that measures airborne particle mass concentration in units of milligrams per
cubic meter (mg/m3).
1.
2.
3.
4.
5.
6.
Locate prepared dust chamber and sample train tubing.
Set up sample train from dust chamber to SidePak.
Shake dust chamber to circulate Arizona Test Dust for sampling and wait 5 minutes.
Press the PAGE key to turn on instrument.
Wait for the concentration to stabilize and record the instrument’s output.
Remove sample train and take a reading from the lab room ambient environment.
BACtrack S80 Professional Breathalyzer
Background:The fuel cell has two platinum electrodes with a porous acid-electrolyte material sandwiched
between them. As the exhaled air from the suspect flows past one side of the fuel cell, the platinum oxidizes any
alcohol in the air to produce acetic acid, protons and electrons.The electrons flow through a wire from the
platinum electrode. The wire is connected to an electrical-current meter and to the platinum electrode on the other
side. The protons move through the lower portion of the fuel cell and combine with oxygen and the electrons on
the other side to form water. The more alcohol that becomes oxidized, the greater the electrical current. A
microprocessor measures the electrical current and calculates the BAC.
%BAC = g/deciliter (dl) of blood, USA assumes a blood:breath ratio of 2100:1.
Example: A standard prepared at 50 ppm of ethanol is measured with a breathalyzer.
breathalyzer output in %BAC?
50ppm -> x mg/m3
𝑥
𝑚𝑔
𝑚3
=
(50𝑝𝑝𝑚)(46.1
𝑙
24.45
𝑚𝑜𝑙
𝑔
)
𝑚𝑜𝑙
What should the
98.4 mg/m3 -> x g/dl (breath)
= 98.3
𝑚𝑔
𝑥
𝑚3
𝑔
𝑑𝑙
= (98.3
𝑚𝑔
𝑚3
)(
1𝑔
1000𝑚𝑔
)(
1𝑚3
10000𝑑𝑙
) = 0.00000983
𝑔
𝑑𝑙
0.00000984 g/dl (breath) -> x g/dl (blood) -> %BAC
𝑥 %𝐵𝐴𝐶 = (0.00000983
1.
2.
3.
𝑔
𝑑𝑙
𝑏𝑟) (
2100
1
) = 0.0206 ~ 0.02 %𝐵𝐴𝐶
Prepare BACtrack S80 sample train by inserting the mouth piece and fit tubing between mouthpiece and
prepared standard bag.
Press START button on BACtrack and wait for countdown to complete and press down on to the
prepared tedlar bag for 5 seconds or until a double beep sound.
Wait and record results.
Gas/Vapor/Particulate Sampling, Calibration, Detector Tubes,
CGM, PID, and Breathalyzer
Questions for Gas and Vapor Sampling
1.
How many microliters are required to make a 100 ppm toluene standard in a 10 liter gas bag? Describe
how the standard is prepared.
2.
What analyte do the detector tubes used actually measure? (Chemical reactions)
3.
How many milliliters did the detector tube piston pump actually draw?
4.
How long did it take to draw the detector tube sample?
5.
What do the CGM and the PID used actually measure?
6.
Explain how the breathalyzer determines Blood Alcohol Content?
7.
How precise were you able to prepare the gas standards? To what do you attribute the variation or errors?
8.
How did the replicate detector tube, CGM, PID and breathalyzer meter readings compare? What factors
would explain the similarities and/or differences?
9.
If a PID reads 10 ppm when measuring an acetone standard, what is the concentration (in ppm) of the
acetone standard? (Assuming a calibrant gas of isobutylene and a response factor for acetone of 5.2
relative to the calibrant gas)
10. Convert a 4000 ppm PID reading for toluene to %LEL.
11. What is the % concentration at saturation for ethanol (vapor pressure of 44 mm Hg) in a room which has
a barometric pressure of 756 mm Hg?
12. Which method would you choose to monitor the vapors (tested in this lab) for compliance with the TLV
or IDLH? Why?
13. What is the appropriate course of action if the data needed to conduct the evaluation is not found in the
NIOSH Pocket Guide or TLV Booklet or TLV Documentation?
14. What concentrations of particulates were detected from the dust chamber and the ambient lab room
atmosphere?
15. How does the laser photometer detect airborne particulate concentrations?