AIRBRUSH AND RATTLE-CAN SAFETY [DRAFT]
Scope: Hobby spraying of acrylics, enamels/oils, and lacquers in small rooms/garages using airbrushes or aerosol (“rattle-can”) paints. U.S.-oriented standards and references.
1. HAZARDS OR WHAT YOU'RE CONTROLLING
- Particles (overspray mist): irritant, lung burden. Captured with filters + airflow.
- Vapors (VOCs/solvents): headache, dizziness; flammability with enamels/lacquers. Managed by ventilation + keeping ignition sources out of the airstream.
- Isocyanates (some 2-pack urethanes): strong sensitizers → occupational asthma; hobbyists should avoid entirely.
- Fire/explosion: flammable aerosols/vapors + sparks/hot motors. Controlled by proper booth/fan/exhaust layout and non-sparking gear.
2. CONTROL HIERARCY OR HOW TO STAY SAFE
Best → OK → Avoid
1. Substitution: Prefer water-borne acrylics over solvent lacquers/enamels where feasible. (Fewer vapors/flammability issues.)
2. Engineering controls (the main event): A local exhaust path that pulls air from the front of the work area, through filter(s), to outside. Keep the fan downstream (on the clean side) if you can, so the motor isn’t in solvent-rich flow.
3. Administrative: Shorter sessions, cure parts in ventilated areas, keep doors/cracks arranged for make-up air (see 4).
4. PPE: For acrylics: P100/HEPA particulate; for enamels/lacquers: NIOSH organic-vapour (OV) + P100 combo. Change cartridges often.
5. Things to avoid: Isocyanates at home; brushing/sparking motors in the solvent plume; recirculating solvent-laden air back into the room.
3. VENTILATION ISSUES THAT MATTER
* Airflow direction: From you → past the part → into the booth opening. Your hands shouldn’t feel “blow-back.”
* Face velocity: Open-face spray booths typically target on the order of ~100 feet per minute (fpm) at the opening to reliably capture mist (exact spec depends on the booth/standard; treat ~100 fpm as a practical benchmark for hobby setups).
* Sizing rule of thumb:
- Measure your booth opening (width × height). Example: 20" × 16" = 2.22 ft².
- Target flow ≈ Area × 100 fpm → ~220 CFM for the example.
- Add margin for filters + duct losses (20–50% more CFM). So spec a fan in the ~275–330 CFM class for that opening. (If you pack dense filters or long flex-duct, add more.)
- Keep static pressure low: Short, smooth duct runs; big gentle bends; avoid crushed flex-duct; change filters before they load up (rising pressure drop = falling capture).
4. ROOM SETUP AND MAKE-UP AIR (the often-missed bit)
- Crack a window/door behind you so the room isn’t starved; starved rooms reverse flow and spill overspray back at you.
- Keep the booth/exhaust path dedicated—don’t tie into HVAC returns.
- Aim the exterior discharge so it can’t drift back in (or onto neighbors).
5. AIRBRUSH VX. RATTLE-CAN: WHAT CHANGES?
- Airbrush (low mass flow): Easier to capture; acrylics + proper booth often adequate with OV/P100 only when using solvents.
- Rattle-can (high mass flow): More paint and propellant → more vapors & flammables. Use maximum ventilation, keep ignition sources away, and step outside if your booth CFM is marginal.
6. FLAMMABILITY AND IGNITION CONTROL (solvent products)
- No open flames/heaters/pilot lights in the spray or exhaust path.
- Don’t put switches or sparking tools in the airflow.
- Ground/bond metal ducting when practical; avoid paint buildup in ducts.
- Know that OSHA 29 CFR 1910.107 and NFPA 33 govern spray finishing with flammables in workplaces; use them as best-practice benchmarks even at home.
7. RESPIRATORS (SIMPLE, CORRECT PICKS)
- Acrylics only: NIOSH P100 (or N95 minimum) for particles; P100 preferred for hobby longevity/fit.
- Enamels/Lacquers: NIOSH OV/P100 (organic vapor + P100).
- Fit matters more than model; replace cartridges on smell/breakthrough or per maker schedule. (OSHA’s ventilation/respirator guidance background.)
8. MATERIALS YOU SHOULD NOT SPRAY AT COME
- Two-pack urethane/isocyanate systems (common in automotive clears, some hardeners). These require professional booths and programs; sensitization can be permanent.
9. HOUSEKEEPING. MAINTENANCE AND WASTE
- Change filters before visible blow-through or heavy loading; bag used filters (they’re fuel-rich) and dispose per local rules.
- Wipe overspray from duct/booth surfaces before it hardens into thick layers.
- Store solvents and solvent rags in metal containers with lids. (EPA best-practices checklists are a useful baseline.)
10. QUICK CHECKLIST
Pre-spray:
- Fan on; feel steady pull into booth front ✔
- Make-up air cracked behind you ✔
- OV/P100 (solvents) or P100 (acrylics) on and sealed ✔
- No flames/heaters/pilots in room ✔
- Test spray: no plume escaping past your face ✔
- Keep fan running 5–10 min to clear vapors ✔
- Bag wipes/filters if saturated ✔
- Close/secure solvent containers ✔
- Inspect filters, duct bends, and fan intake; clean buildup ✔
- Re-measure booth face area × 100 fpm → compare to fan spec; if you added duct/filter resistance, consider more CFM ✔
12. REFERENCES
OSHA 29 CFR 1910.94 & 1910.107 (ventilation; spray finishing with flammables). Good for principles and definitions.
NFPA 33 (2024) — fire/explosion hazard mitigation for spray application; treat as the gold standard. (Overview & standard page.)
OSHA Technical Manual — Industrial Ventilation — fundamentals, troubleshooting airflow.
EPA Safer Choice — Spray Painting Best Practices — concise checklists geared to refinish painting but broadly applicable.
NIOSH/CDC on Isocyanates — why 2-pack systems are a different risk class.
Intro to Industrial Ventilation (Guyer) — readable sizing/back-pressure basics for non-engineers.
