Every safety professional likely has smoke tubes on hand for applications such as respirator fit testing and other airflow identification tasks. However, these smoke tubes can emit a plume of 'smoke' that can cause health and safety issues. These risks can happen if the test is not administered properly, if the test is not carried out in the right environment, or if there's a leak in a respirator that's being fit tested. Hence, there are various precautions to put in place and reactive measures that you should adhere to if something were to go wrong when using a smoke tube(s).

In this post, we take a closer look at smoke tubes, the industries that commonly use these devices, how they factor into respirator fit testing, as well as health and safety tips to follow when smoke tubes are in use.

Smoke Tubes 101: What They Are and What They're Used for

Respirator fit testing is the most common use for smoke tubes. Respirator fit testing ensures that these critical breathing apparatuses can offer the level of intended protection from a worksite's environmental contaminants. Activities such as construction, restoration, abatement, working with hazardous chemicals, working in enclosed spaces, and working in areas with toxic fumes and high dust concentrations typically require the use of a respirator.

However, smoke tubes are also often used to detect airflow, help advise where to place air monitoring equipment, and even help monitor airflow in various locations. Smoke tubes resemble an enclosed glass tube and contain stannic chloride. Stannic chloride turns into smoke when released and exposed in the correct environmental conditions.

How do smoke tubes work? One or both of the ends of a glass tube is opened or broken, and air is drawn through the tube via a rubber bulb. This causes white smoke to emit that is composed of stannic chloride and hydrogen chloride (HCL). Smoke tubes offer a variety of benefits to those that use them however, they can cause some significant problems as well. When improperly used, smoke tubes may cause health and safety issues.

Industries That Commonly Use Smoke Tubes

Because smoke tubes are often used for respirator fit testing and airflow detection, the industries below commonly utilize these devices:

  • Construction
  • Disaster restoration
  • Lab workers
  • Chemical manufacturing
  • Asbestos and lead abatement work
  • Remediation
  • Tank cleaning
  • And more

Smoke Tubes and Respirator Fit Testing

Smoke tubes are an essential item for respirator fit testing. According to OSHA 1910.134 App A, there are four ways to test for respirator safety - and one of these ways just so happens to be the stannic chloride fit test. Stannic chloride qualifies as one of OSHA's designated qualitative and/or quantitative measures. The other three fit test methods require a subjective response from the employee, which many argue could present challenges. Safety professionals rely on the honesty of the person being fit tested, so these subjective test methods are not always as safe.

Irritant smoke testing is not a subjective method. Simply put, the stannic chloride is released in a controlled manner to detect any leakage in the respirator, producing a white smoke and a very pungent odor. It's very easy to tell if an individual encounters the telltale smoke, the odor, or if there's leakage in the respirator throughout testing. Some signs of exposure to watch for include coughing, watering eyes, and skin irritation. In other words, this test doesn't rely on the honesty of a worker.

However, while the smoke tube test is incredibly effective in validating respirator fit testing, one drawback is that the irritant smoke can be dangerous. It's crucial that employers and safety professionals follow the OSHA standard and safety procedures. Smoke tube respirator safety is important to follow to avoid individual harm.

What Respirator Fit Test is the Safest?

Most fit test methods designated in the OSHA 1910.134 App A are subjective. This means a worker could verbally agree to the questions asked in order to get out into the field and begin working. The irritant smoke test is objective—it's easy to tell if there's leakage in the respirator fit by observing the reaction of the individual wearing the respirator.

So which type of fit test is best? It depends. If you trust your workers or if the environment that they'll be working in is somewhat low risk, then any of the subjective measures should suffice. But if you want to make sure that your workers are as safe as possible working in higher risk environments where exposure to contaminants could be harmful or even fatal (i.e., asbestos, lead, carcinogens etc.), then it's best to administer the smoke tube test. This ensures the respirator fits properly so workers are not exposed to the worksite’s hazards whether its toxic fumes, hazardous dusts/particulates, or unstable gasses.

OSHA 1910.134 App A: What You Need to Know

OSHA 1910.134 App A is the regulation that applies to proper fit testing with a full or half-face respirator. This regulation will detail everything that you need to know about carrying out each type of fit test, as well as safety protocols to follow. Refer to this regulation for details on the irritant smoke stannic chloride protocol and all other test methods recognized by OSHA for proper fit testing. Ideally, safety professionals should have this regulation printed out and easily accessible - especially if fit testing is something they frequently perform.

Health and Safety Impact of Stannic Chloride

Stannic chloride can pose a safety threat. This is why it's important to understand how to properly conduct the test, and to ensure the test is conducted in the right conditions, to ensure the proper fit of any respirator that’s tested. Common stannic chloride uses include textile dyeing, use as a bleaching agent, and use in some soaps and cleaning materials. But when stannic chloride reacts with humid air— the ideal conditions for release from the smoke tube—then it becomes what OSHA describes as an "irritant smoke."

Irritant smokes can cause eye, skin, and throat irritation if inhaled, so to avoid any further harm or injury, it's important that irritant smoke respirator tests are carried out in a controlled way. For instance:

  • The smoke tube should be gently pumped via the squeeze bulb toward the individual wearing the respirator.
  • Smoke tubes should be pumped about a foot away from the individual so that the smoke plume surrounds the entirety of the respirator.
  • The tester should then gradually move to about 6 inches away from the individual, making another pass with the smoke plume.
  • If, at any time, the individual begins coughing or reports any sort of sensitivity to the smoke, they should be immediately moved to a place with adequate ventilation. After adjusting the fit to correct any areas of leakage, the test will have to be repeated.
  • If the individual does not report any sensitivity or reaction after the second test, they have passed the respirator fit test.

Health and Safety Impact of Smoke Tubes

There are various other safety guidelines that should be followed when it comes to performing the irritant smoke respirator test. These guidelines include the following:

  • Ensure the test administrator knows what to do and follows OSHA 1910.134 App A guidelines.
  • Do not break or remove the ends of the smoke tube to begin the test until the proper preventative safety precautions are in place.
  • If the individual begins coughing or showing signs of irritation, the fit test should be stopped, and the individual needs to be moved to an area with fresh air.
  • If exposure is significant, eye wash stations and showers should be used.
  • Ensure that the fit test is carried out in an area with adequate ventilation to prevent the buildup of the irritant smoke and to ensure that the individual can retreat to an area of fresh air in the event of a failed fit test.
  • Do not eat, drink, or smoke in any an area with stannic chloride or an area with the potential of containing stannic chloride.

While the smoke tube test is arguably the best way to verify a proper respirator fit, the method is not without its drawbacks. The hazardous nature of stannic chloride smoke is the biggest one. However, in environments where even a small leak could lead to major long-term health consequences, you can't risk any sort of poor-fitting respirator. That's why it's important to know how to properly administer a respirator smoke test and what to do in the event that it fails.