Module 1 Assessment: Abrasive Blasting Fundamentals

Assessment ID: U10-M1-ASSESS Type: Knowledge Quiz + Application Scenarios Duration: 35 minutes Pass Threshold: 80% overall

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Part A: Knowledge Quiz (15 points)

Instructions: Answer all 15 questions. You may use reference materials. One point per correct answer.

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Question 1: Physics of Abrasive Blasting

What physical principle enables abrasive blasting to remove material from surfaces?

Transfer of kinetic energy from high-velocity particles to the substrate material

Chemical reaction between media and surface

Thermal energy from friction melting the surface

Electrostatic attraction between media and substrate

Submit

Explanation: Abrasive blasting works by converting compressed air pressure into particle velocity. When particles strike the surface at high speed, they transfer kinetic energy, causing material fracture and removal.

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Question 2: Crystalline Silica Structure

Why is crystalline silica (quartz) particularly hazardous compared to other minerals?

It is more toxic than other dusts

Its crystal structure is sharp and angular, causing inflammation when inhaled; respirable particles embed in lung tissue

It reacts chemically with lung tissue

It is heavier than other media and causes trauma

Submit

Explanation: Crystalline silica's sharp angular shape and respirable size (< 5 microns) allow particles to penetrate deep into the alveoli. The body's response to the sharp particles is inflammation, fibrosis, and eventual silicosis.

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Question 3: Silicosis Latency

Which statement best describes the latency period for silicosis?

Symptoms appear immediately after first exposure

Symptoms typically appear within weeks to months

Symptoms may not appear for 10–20+ years of cumulative exposure; disease is dose-dependent

There is no latency; disease only develops with a single high-dose exposure

Submit

Explanation: Silicosis is cumulative and slow-developing. The disease progresses through stages (simple → complicated) over years or decades. Even short-term exposure during a maker's early career can contribute to lifetime risk.

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Question 4: OSHA Exposure Limits

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

10 mg/m³ per 8-hour shift

50 μg/m³ (micrograms per cubic meter) per 8-hour shift

100 mg/m³ per shift (no respirable distinction)

There is no limit; worker exposure is voluntary

Submit

Explanation: OSHA reduced the silica PEL to 50 μg/m³ (from 250 mg/m³) effective June 2018, reflecting current science on silicosis risk. This is a very low limit, achievable only with engineering controls (dust collection) and respiratory protection.

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Question 5: Non-Silica Media

Which of the following is a non-silica blasting medium suitable for maker/art spaces?

Quartz sand (crystalline silica)

Glass beads or walnut shell

Feldspar (a silicate mineral, still has some silica)

Limestone (calcium carbonate, but contains respirable dust)

Submit

Explanation: Glass beads (soda-lime glass) and walnut shell are organic/non-crystalline alternatives with lower silicosis risk. Glass beads are durable and reusable; walnut shell is biodegradable but less aggressive.

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Question 6: Dust Collection Requirement

Why is HEPA filtration specifically required for silica blasting operations?

It looks more professional

HEPA filters capture 99.97% of particles > 0.3 microns, essential for trapping respirable silica particles

HEPA filters are cheaper than standard filters

HEPA filters extend media life

Submit

Explanation: Standard vacuum or shop vac filters capture larger particles but miss respirable silica (< 5 microns). HEPA filtration is specifically designed to capture submicron particles, protecting both equipment cleanliness and worker health.

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Question 7: Media Recycling

Which media can be recycled (reused) the most times without significant degradation?

Walnut shell (organic, degrades with use)

Steel shot or glass beads (remain intact through repeated cycles)

Crystalline silica (breaks into smaller respirable fragments with use)

Aluminum oxide (oxidizes and becomes brittle)

Submit

Explanation: Durable, inert media (steel shot, glass beads) can be cycled 50–100+ times before disposal. Organic media (walnut, corn cob) degrade after 3–5 uses. This affects cost and sustainability calculations.

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Question 8: Cabinet Dust Collection

In a sandblasting cabinet, where does dust collection occur?

Only during the blasting operation itself

During blasting (primary collection) and after (continuous circulation to HEPA filter)

Only after blasting, when the operator opens the cabinet

Dust collection is not necessary; dust settles naturally

Submit

Explanation: A proper blasting cabinet has continuous dust collection: (1) negative pressure during blasting pulls dust away from operator, and (2) a recirculation system continuously pulls air through the HEPA filter even after blasting stops, preventing dust accumulation.

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Question 9: Air Compressor Moisture

Why must compressed air be dried (moisture removed) before use in blasting?

Moist air is heavier and reduces blasting pressure

Water in compressed air rusts media and cabinet interior; reduces media flow; contaminates final surface

It is tradition; there is no technical reason

Moist air reduces the worker's comfort

Submit

Explanation: Compressed air from a pump contains moisture (condensation). Without drying (via air dryer or moisture trap), this water causes media clumping and blockages, rust inside the cabinet and media lines, and contamination of blasted surfaces (water spots, corrosion).

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Question 10: Nozzle Types

For detail work (small features, precision blasting), which nozzle design is preferred?

Large-bore nozzle (> 1 inch diameter) for maximum coverage

Small-bore nozzle (3–5 mm diameter) for focused, controlled blasting

Ultra-large nozzle for efficiency

Nozzle size does not matter

Submit

Explanation: Smaller nozzles concentrate the blast stream on a smaller area, allowing precision control and detail work. Larger nozzles spread the blast over a wider area, suitable for aggressive cleanup or large flat surfaces.

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Question 11: Pressure Settings

What is the typical operating pressure for a sandblasting cabinet?

5–10 PSI (very low, ineffective)

20–30 PSI (low pressure, slow work)

80–100 PSI (high pressure, effective material removal)

200+ PSI (excessive, dangerous)

Submit

Explanation: Most hobby/maker cabinets operate at 80–100 PSI compressed air. Professional systems may run 90–130 PSI depending on media and application. Too low pressure = ineffective blasting; too high = excessive noise, rapid media consumption, potential cabinet damage.

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Question 12: Respiratory Protection Classification

What does the "P100" rating on a respirator cartridge mean?

Protects against 100% of all airborne hazards

Protects for 100 hours of use

Filters 99.97% of non-oil particles down to 0.3 microns; rated for "Strongly Hazardous" particulates

Requires 100% fit-test score

Submit

Explanation: P100 cartridges (and N100, R100) are the highest-efficiency particulate filters. The "P" means "Not Oil-susceptible" (good for non-oil-based dusts like silica). This is the minimum for silica blasting operations.

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Question 13: Recycling Media

After media has been used for blasting, what can be done with it?

It must be disposed as hazardous waste

Non-reactive media (steel, glass beads) can be filtered and reused; organic media (walnut) can be composted or disposed

All media must be incinerated

Media can be mixed with potting soil for gardening

Submit

Explanation: Media lifecycle: (1) use → (2) collect in cabinet hopper → (3) filter and separate fines → (4) reuse or dispose. Recyclable media reduces cost and waste; some media (walnut shell, corn cob) is compostable.

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Question 14: Hearing Protection

Sandblasting cabinets typically produce noise at what level?

70 dB (conversational speech)

80 dB (alarm clock)

85–110 dB (loud machinery; hearing protection required for 8-hour exposure above 85 dB)

140 dB (peak exposure causing immediate damage)

Submit

Explanation: Sandblasting cabinets are loud. Sustained exposure above 85 dB (per OSHA 29 CFR 1910.95) requires hearing protection. Double protection (earplugs + earmuffs) is recommended for cabinet operation.

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Question 15: Post-Blasting Cleanup

After completing a sandblasting task, what is the critical cleanup step to prevent ongoing exposure?

Turn off the compressor and open the cabinet door immediately

Leave dust collection running for several minutes after blasting stops to clear residual airborne dust

Allow dust to settle naturally (takes hours)

Vacuum by hand without a HEPA-equipped vacuum

Submit

Explanation: Airborne silica dust can remain suspended for extended periods. Continuing to run dust collection after blasting removes residual particles. Opening the cabinet door prematurely would release trapped dust into the room.