How to Decide Whether a Task Needs a Respirator

Why this matters

Two wrong answers to this question show up on job sites. The first is the bare face on a task that puts a carcinogen in the breathing zone, because the dust settled quickly and nobody coughed. The second is a dust mask handed out "to be safe" on a task where use is actually required, which quietly obligates the shop to a medical evaluation, a fit test and training it never gave. Both come from skipping the same four decisions in order: what the agent is and how much of it there will be, what controls come first, which respirator class covers the remainder, and whether the use is required or voluntary. This card walks those four decisions on one real task, then runs the same gate against a second task that lands the other way.

The vocabulary (agent, route, dose, exposure limit) is owned by a sibling card; Dose, Route and the Exposure You Cannot See.

Step 1: Name the agent and estimate the exposure

Name the agent first, in writing. "Dust" is not an agent. Lead in paint, crystalline silica in masonry, a solvent in a sealant, asbestos in an old floor tile: each has its own limit, its own standard and sometimes its own respirator rules. Get the identity from the SDS for products, and from a test (a paint chip result, a bulk sample, a lead test kit recognized for the purpose) for materials already in the building.

Then find the limit. OSHA's permissible exposure limit (PEL) is the enforceable floor. The NIOSH recommended exposure limit (REL) is advisory and often lower, and many shops decide against the stricter of the two. Write down the number and its averaging time, usually an 8-hour time-weighted average.

Then estimate the exposure, from the best source you have. In order of strength:

• Personal air sampling on your own crew doing this task, collected and analyzed by an industrial hygienist or an accredited lab.
• Objective data: published or industry-generated measurements for the same task, material and controls.
• A presumption the standard itself sets. The construction lead standard does this: 29 CFR 1926.62(d)(2) lists tasks presumed to exceed the PEL until the employer's own assessment shows otherwise. The construction silica standard does something similar through Table 1 at 1926.1153(c); see related: Respirable Crystalline Silica and the Construction Standard.
• Judgment, which is not an estimate. If judgment is all you have, the honest output of this step is "unknown," and the next steps treat unknown as high.

On the plaster job. A handyman crew is removing a painted plaster wall in a 1940s house so an electrician can run new circuits. A paint chip test came back positive for lead. The agent is lead. The PEL under the construction lead standard is 50 micrograms per cubic meter as an 8-hour TWA, with an action level of 30. Manual demolition of a lead-painted surface is on the 1926.62(d)(2)(i) presumption list, which presumes exposure above the PEL and within the band up to 500 micrograms. No sampling has been done on this crew. The estimate is the presumption.

What breaks if you skip this: without a number you cannot pick a respirator class in Step 3, and you will pick by habit.

Step 2: Apply the controls before the respirator

A respirator protects one person, depends on fit and behavior, and fails silently. So it goes last. Work down the hierarchy (owned by a sibling: see related: The Hierarchy of Controls on a Service Call): can the task be avoided, the material swapped, the dust captured at the tool, the space ventilated, the time shortened?

On the plaster job. Elimination is not available; the wall has to come out. The crew applies what it can: misting the plaster before and during removal so it comes down damp, plastic sheeting over the doorway and floor with the HVAC return in that room sealed, a HEPA vacuum for debris instead of a broom, and bagging debris at the wall rather than carrying it through the house. Occupant protection under the EPA renovation rule is a separate duty with its own card; Lead Paint RRP Contractor Rules.

Here is the trap. Those controls almost certainly lowered the real exposure, and they do not change the respirator answer yet. The presumption in 1926.62(d)(2) stands until the employer has an exposure assessment showing otherwise, so the interim protection, respirators included, applies while the controls are in place. The way to earn a lower answer is to sample this crew doing this task with these controls, not to assume the misting worked.

What breaks if you skip this: you buy a respirator to cover dust a misting bottle would have kept on the floor, or you conclude the controls are enough without a measurement that says so.

Step 3: Pick the respirator class from the protection factor

Every respirator type has an assigned protection factor (APF): the workplace level of protection a properly functioning, properly fitted respirator is expected to provide to trained users. OSHA sets them in Table 1 at 29 CFR 1910.134(d)(3)(i)(A). The ones a service shop meets most:

The maximum use concentration is the APF times the exposure limit. If the exposure estimate is above that, the respirator is not enough.

CALCULATION SHEET - plaster wall removal
Agent: lead          Limit: PEL 50 ug/m3, 8-hr TWA
Estimate: presumed band, top at 500 ug/m3
Protection needed: 500 / 50 = 10

Half mask, APF 10:  max use 10 x 50 = 500 ug/m3
Full face, APF 50:  max use 50 x 50 = 2,500 ug/m3

Selected: elastomeric half mask, 100-series
particulate filters (lead is a particulate)
Use status: REQUIRED by 1926.62 -> full program

The half mask exactly covers the top of the presumed band. The crew could choose a full facepiece for margin, and the lead standard has its own rule worth knowing: under 1926.62(f), an employee who asks for a powered air-purifying respirator gets one when it gives adequate protection.

Two limits the table does not show. An air-purifying respirator does not supply oxygen, so a space that may be oxygen deficient (a crawlspace after a nitrogen pressure test, a pit with refrigerant pooled in it) is never an APF question; see related: Nitrogen Purging and the Air You Cannot Smell. And a concentration immediately dangerous to life or health calls for supplied air under 1910.134(d)(2), which is outside what this card covers. For gases and vapors, the cartridge also needs a change schedule; see related: Filter and Cartridge Selection in Plain Terms.

What breaks if you skip this: a half mask goes onto a task presumed above 500, such as one on the 1926.62(d)(2)(ii) list, and the crew is protected to a level the respirator was never rated for.

Step 4: Decide whether the program applies

This is the step that decides what the shop owes, and the rule is short. Under 29 CFR 1910.134(a)(2), when a respirator is necessary to protect health, the employer must provide it, and under 1910.134(c)(1) the employer must run a written respiratory protection program for any employee required to wear one. Construction work reaches the same standard through 1926.103. A required use means all of it:

• a medical evaluation before the fit test and before use, under 1910.134(e);
• a fit test on the exact make, model, style and size before use and at least every 12 months, under 1910.134(f); see related: OSHA Respiratory Protection - Annual Fit Test;
• training before use and at least annually, under 1910.134(k);
• a clean-shaven seal surface, under 1910.134(g)(1)(i), and a user seal check every time it goes on; see related: How to Do a User Seal Check Every Time.

On the plaster job, use is required, because the lead standard's interim protection requires it on a presumption task. So the crew members need medical clearance and a current fit test on the half mask they will wear before demolition starts. If one of them has not been fit tested on that mask, that person does not do the demolition; reassigning them to the debris run outside the containment is the honest answer, not lending them a mask. The lead standard also makes blood lead sampling part of the interim protection on presumption tasks; see related: Lead Exposure for the Worker, Not the Occupant.

The second task: same crew, the other answer

The following week the same crew blows loose-fill cellulose into an attic in a 2000s house. Run the same four steps.

Step 1. The agent is cellulose fiber dust with the product's borate treatment. The SDS lists no specific OSHA standard; the dust falls under the general particulate limits for particulates not otherwise regulated. The manufacturer's data and the crew's experience put the exposure well under those limits with the machine running outside and the hose in the attic. Step 2. Controls: the machine stays outdoors, the attic hatch is the only opening, and the crew rotates the hose position. Step 3. No respirator is needed to stay under the limit on this estimate. Step 4. Two of the crew still want filtering facepieces because the dust is unpleasant. That is voluntary use, and it carries its own lighter set of duties, starting with handing each of them the Appendix D information sheet; see related: Voluntary Respirator Use and What the Shop Still Owes.

What would flip this task: the SDS on a different product listing a fiber or a binder with its own limit, an attic with old vermiculite in it (which may contain asbestos and stops the job), or a shop rule that everyone wears a respirator on insulation work. That last one matters more than it looks: a respirator the shop requires is required use, whatever the measured exposure, and the full program applies.

How to verify you got this right

• The decision is written: agent, limit, estimate and its source, controls applied, APF arithmetic, and use status. A reader months later can see why.
• The estimate's source is honest. "Presumed per 1926.62(d)(2)(i)" or "personal sample, date, lab" is a source. "Experience" is not, and the record should say "unknown, treated as high."
• Every required user has a medical clearance and a fit test on file for the exact respirator, dated within 12 months, before the task starts.
• Where the estimate was a presumption, there is a plan to sample. That is how a crew earns its way to a lower class or off the respirator entirely.

References

• OSHA, 29 CFR 1910.134 Respiratory Protection (Table 1 assigned protection factors at (d)(3)(i)(A)); 29 CFR 1926.103 applies it to construction
• OSHA, 29 CFR 1926.62 Lead in Construction ((d)(2) presumed exposures and interim protection)
• NIOSH, Respirator Selection Logic
• See related: OSHA Respiratory Protection - Annual Fit Test
• See related: The Hierarchy of Controls on a Service Call