Module 3: Assessment Quiz

Module: U10M3 - Respiratory Protection and Ventilation Duration: 20-30 minutes Passing Score: 70%

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What is the OSHA Permissible Exposure Limit (PEL) for respirable crystalline silica?

50 μg/m³ as an 8-hour TWA

500 μg/m³ as an 8-hour TWA

5 mg/m³ as an 8-hour TWA

0.5 μg/m³ as an 8-hour TWA

Submit

Explanation: OSHA's PEL for respirable crystalline silica is 50 micrograms per cubic meter of air (50 μg/m³) averaged over an 8-hour time-weighted average (29 CFR 1910.1053). This was reduced from the previous 250 μg/m³ in 2016.

What is the minimum respiratory protection required when operating a blast cabinet with functional dust collection?

N95 filtering facepiece respirator

No respiratory protection needed

Supplied Air Respirator (SAR)

Self-Contained Breathing Apparatus (SCBA)

Submit

Explanation: Even with functional cabinet dust collection, an N95 filtering facepiece is the minimum requirement. Cabinet seals are not perfect, and media changes and cleanup generate dust exposure.

What does the "95" in N95 mean?

Filters at least 95% of airborne particles 0.3 microns and larger

Protects for 95 minutes of use

Rated for 95 PSI maximum pressure

Contains 95 layers of filter material

Submit

Explanation: The "95" designation means the filter captures at least 95% of test aerosol particles (0.3 μm NaCl). The "N" means Not resistant to oil. P95 and R95 variants provide oil resistance.

What is the purpose of a user seal check when donning a respirator?

To verify the respirator is properly seated against the face with no leaks

To test the filter for manufacturing defects

To measure the oxygen level inside the respirator

To calibrate the exhalation valve

Submit

Explanation: A user seal check (positive and negative pressure tests) verifies that the respirator seals against the face. Without a proper seal, contaminated air bypasses the filter through gaps — the respirator provides no protection.

What Assigned Protection Factor (APF) does a properly fitted half-face elastomeric respirator provide?

APF 10 (reduces exposure by a factor of 10)

APF 2 (reduces by factor of 2)

APF 50 (reduces by factor of 50)

APF 1000 (reduces by factor of 1000)

Submit

Explanation: Half-face elastomeric respirators have an APF of 10, meaning they reduce airborne contaminant concentration by a factor of 10. Full-face respirators provide APF 50. Supplied-air systems provide APF 1000+.

Which factor renders an N95 respirator ineffective?

Facial hair that interferes with the face seal

Cold ambient temperature

Wearing safety glasses simultaneously

Using the respirator for more than one hour

Submit

Explanation: Facial hair (beards, stubble) between the sealing surface and the face creates leak paths that bypass the filter. OSHA requires that respirator users be clean-shaven in the seal area. Stubble as short as one day's growth can compromise the seal.

What is the primary function of a local exhaust ventilation (LEV) system on a blast cabinet?

To capture airborne dust at the source before it enters the operator's breathing zone

To cool the compressed air supply

To recirculate media faster

To increase cabinet pressure

Submit

Explanation: LEV systems capture contaminants at or near the point of generation — the blast cabinet interior. By maintaining negative pressure inside the cabinet, dust is drawn away from the operator rather than escaping through seals and openings.

How is dust collector filter condition typically monitored?

By reading the differential pressure gauge across the filter

By weighing the filter monthly

By visual inspection only

By measuring the temperature of exhaust air

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Explanation: A differential pressure (ΔP) gauge measures the pressure drop across the filter. As the filter loads with dust, ΔP increases. Most manufacturers specify filter replacement when ΔP exceeds 4-6 inches of water column.

What minimum capture velocity is recommended at the opening of a blast cabinet exhaust duct?

200-500 feet per minute (fpm)

10-20 fpm

50-100 fpm

2000-5000 fpm

Submit

Explanation: ACGIH recommends 200-500 fpm capture velocity for abrasive blasting enclosures. This velocity is sufficient to overcome the turbulence generated by the blast stream and capture particulates before they escape.

When is a Supplied Air Respirator (SAR) required instead of a filtering facepiece?

When performing open blasting outside a cabinet, or when airborne concentrations exceed the APF of filtering respirators

Whenever any blasting is performed

Only when using silica sand

Only in outdoor environments

Submit

Explanation: Open (non-cabinet) blasting generates extremely high particulate concentrations that exceed the protection factor of filtering respirators. OSHA requires SAR with abrasive blasting hood for any open blasting operation. Cabinet blasting with functional LEV generally allows filtering facepieces.

How often must respirator cartridges/filters be replaced?

When breathing resistance increases noticeably, or according to manufacturer's change schedule

Once per year

Only when visibly damaged

After every single use

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Explanation: Filter cartridges load with particulates over time, increasing breathing resistance. Replace when resistance becomes noticeable, when the filter is damaged or contaminated, or per the manufacturer's recommended schedule — whichever comes first.

What ventilation duct velocity is recommended to prevent particulate settling in horizontal runs?

3500-4500 feet per minute minimum transport velocity

500-1000 fpm

100-200 fpm

10,000+ fpm

Submit

Explanation: The minimum transport velocity to keep abrasive dust entrained (not settling) in horizontal ductwork is 3500-4500 fpm per ACGIH guidelines. Below this velocity, particulates settle and accumulate, reducing system effectiveness and creating a fire/explosion hazard.