Textile dyehouses work with flammable solvents like ethanol, isopropanol and toluene. Spray booths, drying ovens and solvent storage fall under NFPA 33 (Spray Application) and NFPA 86. Solvent vapor accumulation on fabric creates Class I Div 1 hazardous areas.
Spray Booth Design
- Airflow: 0.5 m/s (100 fpm) cross-section
- Enclosure: non-combustible metal (0.9 mm steel)
- Filter bank: overspray trap, weekly change
- Fan: spark-resistant (non-ferrous blade)
- Interlock: fan fault - stop spray
Solvent LEL and Ventilation
- Ethanol LEL: 3.3 percent (61,000 ppm)
- Toluene LEL: 1.1 percent (11,000 ppm)
- Operating limit: 25 percent LEL max
- Ventilation: 30 m3/min/m2 booth area
- LEL detector: 10 percent alarm, 25 percent shutdown
NFPA 33 Sprinkler and Extinguisher
- Booth sprinkler: OH2, K=8, 15 L/min/m2
- Duct sprinkler: every 4 m in exhaust duct
- Portable: 20B:C CO2 per 10 m
- Dry chemical: automatic booth protection (ABC)
Class I Div 1 and Electrical
- Booth interior: Class I Div 1 (NFPA 70)
- 1 m outside booth: Class I Div 2
- 3 m outside: non-classified
- Lighting: explosion-proof LED (UL 844)
- Static bonding: 1 ohm max resistance
Dyehouse ventilation with MEP Calc
MEP Calc sizes dyehouse booth airflow, LEL monitoring and makeup air per NFPA 33.
Download MEP Calc on the App Store
Sources & Further Reading
NFPA 33, NFPA 86, NFPA 70 Art 516, OSHA 29 CFR 1910.107, EPA VOC regulations. NFPA 33 Spray Application standard.