In April, the US Coast Guard released a Marine Safety Alert on confined space risks and the need for training and emergency rescue procedures. The reminder came after three people were asphyxiated while working in manholes on a mobile offshore drilling unit.

We feel it’s the right time to tackle respiratory selection for the invisible killer inside confined spaces – air—or the lack of. Namely, we’ll debate the “why” and “when” to choose SCBA compared to other respiratory protective equipment when working in these confined spaces.

Why choose an SCBA

Whether it’s maintaining and cleaning tanks or reactors, repairing gas lines in trenches, working in sewers, storage tanks, pipelines - choosing an SCBA over another respiratory solution depends, first and foremost, on the application.

The decision should take into consideration the following questions and answers:

1.       Does the confined space contain a respiratory hazard?

2.       Has air monitoring been performed?

3.       Have toxic gases or vapors been identified?

4.       What is the oxygen level?

5.       Can I control or eliminate the hazards?

6.       Do I need additional air monitoring?

7.       What are the rescue and emergency plans in place?

Anyone using a respirator in a permit-required confined space will need to follow OSHA, CSA and local regulations where applicable.

In all circumstances, such as entry and escape in confined spaces, the National Institute of Occupational Safety and Health (NIOSH) approves the equipment and how it’s used. For instance, SCBAs used for structural firefighting are also certified to National Fire Protection Association standard 1981.

OSHA’s regulation for Permit Required Confine Space, 29 CFR 1910.146, and Canada’s standard, Z1006.6-16 outline the general guidelines for confined space including air monitoring. Both refer to each country’s specific respiratory regulations for respiratory protection guidelines. The US respirator selection is determined by 29 CFR 1910.134 and Z94.4-11.

Respirator selection is determined by many factors, including whether the contaminants can be identified, the concentration of the contaminants if known, and the level of oxygen. Many gases and vapors have a concentration level that has been identified as Immediately Dangerous to Life and Health (IDLH). If the oxygen content is below 19.5%, it is considered IDLH. When working in confined spaces, if the concentration or oxygen level is unknown or can’t be controlled by engineering methods, it must be assumed that that confined space is IDLH.

OSHA and CSA require the use of a self-contained breathing apparatus (SCBA) or a pressure-demand supplied-air respirator (PD-SAR) with emergency escape if the environment is IDLH or unknown.

Air-purifying vs. SCBA and PD-SAR

SCBAs offer the highest level of protection. These respirators include a cylinder filled with breathable air and are available in 30 minute, 45 minute and 60 minute rated duration. They supply air “on demand”— namely, as the user inhales air flows into the facepiece. Because the flow of air will vary depending on the worker’s breathing rate, the actual service time will be much less than the rated duration. It is not unusual for a 30-minute unit to only provide 15 minutes of actual worktime. For this reason, a supplied-air system may offer a better solution.

PD-SARs are connected to breathing air with up to 300’ of hose. Like the SCBA system, the air flows to the facepiece on demand, as the worker inhales. There are two types of PD-SAR. One version does not include an escape cylinder. The other version includes a 5 or 10-minute rated cylinder for escape only. This second version can be used for entry and work in an IDLH environment.

Air-purifying respirators are small, light, cost-effective and simple in operation. However, these respirators can’t be used in IDLH or oxygen-deficient atmospheres.

So, which respirator is the right one to use for your confined space application?

If the contaminate concentration is IDLH or unknown, or the oxygen is below 19.5% the best solution is SCBA or PD-SAR with escape.

If you don’t need to wear an SCBA or PD-SAR with escape, solutions include airline respirators, whether PD-SAR or continuous flow, powered air-purifying respirators, or APR, depending on the permissible exposure limits (PEL). Refer to OSHA 20 CFR 1910.134 or CSA Z94.4-11 for information on using the right respirator.

Also, consider the need for mobility versus how long the worker will be in the confined space. If the situation requires a supplied-air respirator, yet being tethered to a breathing air hose is too cumbersome or not practical, an SCBA in the answer. Bear in mind, SCBA service life is limited by cylinder duration, so turn to supplied air for work durations of an hour or more.

If the worker does not need supplied air or SCBA, PAPR or air-purifying respirators offer the best mobility, loner work duration, and ease of use.