We’ve all heard stories of tragic incidents that have resulted in the deaths or permanent impairment of employees who were working in confined spaces. A majority of these tragedies could have been prevented with proper training and the use of adequate safety equipment, particularly respiratory protection.

But before we begin a discussion on using respiratory equipment in confined spaces, it is essential to have a basic understanding of the key definitions and concepts of confined-space work.

Tight quarters

First, let’s make sure we all know what constitutes a confined space. A confined space is defined as an area that:

1) is large enough and so configured that a person can bodily enter and perform assigned work;

2) has limited or restricted means for entry or exit (such as tanks, vessels, silos, storage bins, hoppers, vaults and pits); and

3) is not designed for continuous employee occupancy.

Confined spaces are categorized as non-permit-required or permit-required. Non-permit-required confined spaces typically do not have atmospheric hazards or the potential to contain any hazard that is capable of causing death or serious physical harm. Also, if the hazard can be controlled through engineering (ventilation), it can be considered a non-permit confined space. This can be determined using gas detection equipment.

A permit-required confined space:

1) contains or has the potential to contain a hazardous atmosphere;

2) contains a material that has the potential for engulfing an entrant;

3) has an internal configuration such that an entrant could be trapped or asphyxiated by inwardly converging walls or by a floor which slopes and tapers to a smaller cross-section; or

4) contains any other recognized serious safety or health hazard.

How’s the atmosphere?

Before beginning confined-space work, you must assess the internal atmospheric conditions of the work space.

OSHA standards mandate that the area must be tested with a calibrated, direct-reading multi-gas instrument for the following conditions in the order given: 1) oxygen content; 2) flammable gases and vapors; and 3) potential toxic air contaminants. If the confined space is considered to be immediately dangerous to life or health (IDLH) or potentially IDLH, OSHA requires any worker entering the space to have the minimum respiratory protection of a pressure-demand air-supplied respirator system with an egress bottle.

After the atmosphere of a confined space has been analyzed, it is time to select the proper respiratory protection equipment for all entrants working within it.

Which respirator?

Types of respirators recommended for permit-required confined-space operations include a self-contained breathing apparatus (SCBA) or a combination air-line respirator with an egress cylinder.

Because these devices vary in design, application and protective capability, it is important to first assess the level of contaminants at the work site. The level of the hazard will determine the type of respiratory protection. Many respiratory equipment manufacturers have tools or software that can aid in the selection of equipment based on the concentration levels of contaminants. Equally important in ensuring proper selection of various respiratory protection devices is up-to-date knowledge of their limitations.

Self-Contained Breathing Apparatus (SCBA) — These provide the highest level of respiratory protection and are designed to protect workers in oxygen-deficient atmospheres and/or in IDLH atmospheres often found in confined spaces. SCBA are equipped with a user-worn air cylinder that offers a dependable yet limited supply of air without any hoses or tethers to limit movement.

SCBA are useful in confined spaces with entrances large enough to accommodate both the entrant wearing the apparatus and the cylinder. Low-profile cylinders are available for particularly tight confined-space entrances. The cylinder service time ranges from 30, 45 or 60 minutes. SCBA that meet the NFPA 1981–2002 compliance have a feature that allows for rapid filling of the cylinder in emergency situations. Each SCBA is equipped with a fitting that enables the user to connect to a high-pressure air source to fill the cylinder so that he/she can potentially stay in that environment for an extended period of time.

Combination-Type Dual-Purpose SCBA — These devices merge the capabilities of an air-line unit with those of an SCBA. They differ from conventional SCBA in that they generally have a regulator with two inlet ports. One connects to the SCBA air cylinder, the other connects to an air-supply hose. These versatile units offer the mobility of an SCBA when used without the air line, but they also offer an extended air supply when used with the air line, making them especially suited for confined-space applications.

Air-Line Respirators with Egress Cylinders — These units also “combine” the capabilities of an air-line device with those of an SCBA. However, they are generally equipped with smaller (5- or 10-minute) cylinders and are used for emergency escape purposes only. These units provide the lowest profile of any IDLH-approved respirator and are useful when workers must enter and work in extremely tight spaces.

Because of the increased likelihood of oxygen deficiency and the possibility of concentrations of contaminants in confined spaces suddenly changing or not being fully known, air-purifying respirators should not be used for confined-space entry unless known conditions exist and can be maintained.

What type of work?

Determining the type of work being done is an important factor in making respiratory equipment selection. If confined-space entry is for a short term (less than 30 minutes), an SCBA may be the best choice. When the work will take longer than 30 minutes to complete, an SCBA with dual-purpose capabilities or an air-supplied system with egress bottle may make the most sense.

Of course, a respiratory protection program must be established and followed in order to maintain the proper levels of safety. Your firm should adopt a sound respiratory protection program long before doing any work within a confined space.

Confined spaces can be dangerous in every sense. Knowing as much as possible about each particular space and its potential dangers, and taking all necessary precautions before and during work performed within it, will help protect all involved.

SIDEBAR: Before you enter…

Let’s review the basics of respiratory protection for confined-space work:

1) First, determine the type of confined space: non-permit-required or permit-required.

2) If it is a permit-required confined space, assess the nature of the work. The type of work will influence the type of respirator selected.

3) Be sure to provide workers the proper training.

4) Follow the guidelines established in your respiratory protection program.