Air Sampling

This article serves two purposes.

First, it provides descriptions of the more straightforward air sampling concepts and procedures.

Second, if an air sampling method involves more details such that it needs its own article, this page will act as a hub for those additional methods.

One thing to remember: A large amount of this information came from, and can be found in, the OSHA Technical Manual (OTM) Section II Chapter 1. Certain sections of the OTM were updated as recently as at least 2014, including this chapter on air sampling.

Arrangements of Sampling Train

TO DO: Explain, with pictures, the sampling train for regular setups and, especially, low-flow setups.

Carbon Monoxide (CO)

Carbon monoxide is sampled with the ToxiRAE Pro. Refer to its article for information on sampling for CO.

Charcoal Tubes

Charcoal Tube Diagram


  • Just before sampling, use a scorer/breaker tool to uniformly break the ends of the sorbent tube to a 2 mm diameter or half the diameter of the tube body.
  • Keep the tube in a vertical position during sampling to prevent the possibility of channeling that can lead to under-sampling.
  • The arrow on the tube indicates air flow direction and should point to the tube holder and pump. If no arrow is present, the smallest section should be near the tube holder.


The impinger is used when no solid medium is available to "catch" the analyte and must, therefore, be dissolved in a liquid medium. The air from the work environment is passed (as bubbles) through the liquid medium at a rate slow enough to allow the analyte to dissolve and/or react with the medium.

Because a liquid medium is involved, much more consideration must be put into placing this on the employee or in the work area. In some cases, the liquid medium is a corrosive acid. Furthermore, the impinger is made of glass. It is recommended to watch the employee as much and as closely as possible to ensure nothing the employee does will endanger the impinger, its contents, and, ultimately, the employee.

Video demonstrating setup and usage.


TO DO: Enter Isocyanate sampling methods and info about solvent stability.

Low Flow Sampling

Visit the Low Flow Sampling page for information.

Mold Sampling


Time 2 Hours
Media MCEF in 37mm filter cassette
Flow Rate 2 L/min
Tubing Use a short length of tubing — just long enough to be able to flex so the cassette inlet points down.
  • The intake on the cassette always needs to be facing down so that other, heavier particles will not land on the filter.
  • One pump is used outside to get the CFU count for the facility's surrounding environment.
  • One or more pumps are placed inside around the areas of concern.


  • When results come back with a significantly higher fungus count (CFU/m³) for the inside as opposed to the outside count, a letter is sent to the company contact detailing the findings, the hazards, and remediation. Click here to download the letter template.
    • The CSHO compiles a draft letter, which is printed out and submitted in the report under the IB tab.
    • The digital original is sent to your supervisor so that it can be passed on to an admin for revising the date and for review by the Program Manager.

Total Spore Counts vs. Colony Forming Units (CFU)

From "Smells moldy in here" -

Air sampling methods can be divided into two different categories: methods generating “total spore counts,” typically reported as counts per cubic meter (m3) and methods that determine “culturable fungi,” typically reported as colony forming units (CFU) per cubic meter. Total spores counts are an amalgamate of both living and nonliving spores. These methods do not allow for the discrimination between living or dead spores. Culturable fungi results, tabulate only living fungal particles, which can include hyphal fragments as well as spores.

Sampling for total spore counts can be carried out using specially-greased slides and a Burkard or Allergenco sampler. Initial costs for these devices are high but subsequent purchases of greased slides are relatively inexpensive. The principal behind each of these devices is the same; air is vacuumed through and condensed onto the greased slide. Particles in the air are forced onto the grease, become embedded, and stick to its surface.

A more common approach would be to use your own vacuum pump with specially-designed, single-use spore-trap cassettes. Some of the popular cassettes on the market include the Cyclex-d, Air-O-Cell, Microcell5, and the Laro100. Particles in the air are trapped in the cassette either on a proprietary adhesive or, as in the case of the Laro100, a 0.8-micron (mm) filter. The cassettes are opened, prepped and examined under a microscope in a laboratory by properly trained analysts who determine the total spore count. Depending upon your specific complaint or scenario, it may not be important to know the viability of a spore, since dead spores are also potentially allergenic or toxigenic to susceptible individuals.

Nitrogen Dioxide (NO2)

Nitrogen dioxide is sampled with the ToxiRAE Pro. Refer to its article for information on sampling for NO₂.

Respirable Dust – Cyclone

Dorr-Oliver Cycone in an MSA Sampling Train
Media PVC (pre-weighed) in two-piece 37mm filter cassette
Flow Rate 1.7 L/min
Volume Minimum:


Calibration Refer to the Calibration page


  • Using a Cyclone eliminates all particles but respirable particles.
  • Respirable particles are those particles in the size range which would be deposited in the gas exchange region of the lung. Particles too large to be inhaled are collected in a grit pot on the cyclone. The respirable fraction is captured on a pre-weighed PVC filter for gravimetric analysis.
  • Appendix B to OTM Section II: Chapter 1 lists dusts for which respirable sampling should be performed.


There are several methods KYOSH uses to screen for substances. These include:

When screening for substances with a direct read device, results are recorded on an OSHA-93 Direct Reading Report form, which details each location screened and results.

Additionally, an OSHA-98 Screening Report form should be completed for all screened substances.

[Why both of them? I don't know why, but that's what DM says. :) ]

Welding & Arc Cutting Fumes

Welding Helmet Adapter Tubing
Media MCEF
  • 25 mm filter cassette if wearing welding helmet
  • 37 mm filter cassette otherwise
Flow Rate 2 L/min
Volume Minimum: 480 L

Maximum: 960 L

Tubing Helmet Adapter (Refer to image)


The usual purpose for sampling welding and arc cutting fumes is the determination of exposure to metal fumes. Most metals have PELs for the element itself. However, there are two metals which have a PEL not for the element but for an oxide of the metal:

  • iron, as trivalent iron Fe(III) in Fe₂O₃; and
  • zinc, as divalent zinc Zn(II) in ZnO.

Furthermore, there are some metals that have expanded standards, such as lead and hexavalent chromium — Cr(VI). Refer to their specific pages for sampling guidelines. Please note that, in the case of sampling for fumes of chromium, all valences of chromium will be detected using this method — Cr(II), Cr(III), and Cr(VI). There is no way to use this method to single out the individual valences.

Manganese is only limited by a Ceiling value. As far as compliance goes, there is no need to calculate the TWA. However, to be thorough, there is no harm in calculating the TWA and including it in your report but not on your OSHA-91(S) result lines.

Article To-Dos

  • Add Sampling Method numbers and links to each of the tables.