There are five (5) basic types of ventilation systems:
- dilution and removal by general exhaust;
- local exhaust;
- makeup air (or replacement);
- HVAC (primarily for comfort); and
- recirculation systems
Most ventilation systems generally involve a combination of these types of systems. But there are some specific requirements, that need to be met:
This list includes some, but not necessarily all, OSHA standards that address the control of employee exposure to recognized contaminants.
29 CFR 1910.94(a) Abrasive blasting
29 CFR 1910.94(b) Grinding, polishing, and buffing operations
29 CFR 1910.94(d) Open surface tanks
29 CFR 1910.252(c)(2)(i)(a) and (b); (c)(2)(ii) Ventilation for general welding and cutting–General
29 CFR 1910.252(c)(3) Local exhaust hoods and booths
29 CFR 1910.252(c)(5)(ii) Fluorine compounds–Maximum allowable concentration
29 CFR 1910.252(c)(12) Cutting of stainless steels
29 CFR 1910.1003 to .1016 Carcinogens
29 CFR 1910.1025(e)(5) Lead
29 CFR 1910.1027(f)(3) Cadmium
This list includes some, but not necessarily all, OSHA standards that do not contain airflow requirements but are located in the health-related ventilation standards.
29 CFR 1910.94(a)(3)(i)(d) Abrasive blasting–Blasting cleaning
29 CFR 1910.94(a)(5) Abrasive blasting–Personal protective equipment
29 CFR 1910.94(a)(6) Abrasive blasting–Air supply and air compressors
29 CFR 1910.94(a)(7) Abrasive blasting–Operational procedures and general safety
29 CFR 1910.94(d)(9) Open surface tanks–Personal protection
29 CFR 1910.94(d)(10) Open surface tanks–Special precautions for cyanide
29 CFR 1910.94(d)(11) Open surface tanks–Inspection, installation and maintenance
29 CFR 1910.94(d)(12) Open surface tanks–Vapor degreasing tanks
This list includes some, but not necessarily all, OSHA standards that are intended to prevent fire and explosions.
29 CFR 1910.94(c) Ventilation–Spray finishing operations
29 CFR 1910.103(b)(3)(ii)(b) Hydrogen–Gaseous hydrogen systems–Separate buildings
29 CFR 1910.103(b)(3)(iii)(b) Hydrogen–Gaseous hydrogen systems–Special rooms
29 CFR 1910.103(c)(3)(ii)(b) Hydrogen–Liquid hydrogen systems–Separate buildings
29 CFR 1910.103(c)(3)(iii)(b) Hydrogen–Liquid hydrogen systems–Special rooms
29 CFR 1910.104(b)(3)(xii) Oxygen–Bulk oxygen systems–Ventilation
29 CFR 1910.104(b)(8)(vii) Oxygen–Bulk oxygen systems–Venting
29 CFR 1910.106(d)(4)(iv) Flammable and combustible liquids–Container and portable tank storage–Design and construction of inside storage room–Ventilation
29 CFR 1910.106(e)(3)(v) Flammable and combustible liquids–Industrial plants–Unit physical operations–Ventilation
29 CFR 1910.106(f)(2)(iii)(a) Flammable and combustible liquids–Bulk plants–Building–Ventilation
29 CFR 1910.106(h)(3)(iii) Flammable and combustible liquids–Processing plants–Processing building–Ventilation
29 CFR 1910.107(b)(5)(i) Spray finishing using flammable and combustible materials–Spray booths–Dry type overspray collectors
29 CFR 1910.107(d)(1) and (2) Spray finishing using flammable and combustible materials–Ventilation–Conformance–General
29 CFR 1910.107(i)(9) Spray finishing using flammable and combustible materials–Electrostatic hand spraying equipment–Ventilation
29 CFR 1910.108(b)(1) and (2) Dip tanks containing flammable combustible liquids–Ventilation–Ventilation combined with drying
29 CFR 1910.307 Hazardous (classified) locations
Special Conditions Standards – This list includes some but not necessarily all OSHA standards that involve confined space operations and/or high-hazard contaminants specifically designated in the standard.
29 CFR 1910.252(c)(2)(i)(c) Welding, cutting and brazing–Health protection and ventilating–Ventilation for general welding and cutting–General
29 CFR 1910.252(c)(4) Welding, cutting and brazing–Health protection and ventilating–Ventilation in confined spaces
29 CFR 1910.252(c)(5)(i) Welding, cutting and brazing–Fluorine compounds
29 CFR 1910.252(c)(6)(i) Welding, cutting and brazing–Zinc–Confined spaces
29 CFR 1910.252(c)(7)(i) Welding, cutting and brazing–Lead–Confined spaces
29 CFR 1910.252(c)(8) Welding, cutting and brazing–Beryllium
29 CFR 1910.252(c)(9) Welding, cutting and brazing–Cadmium
29 CFR 1910.252(c)(10) Welding, cutting and brazing–Mercury
Troubleshooting an Exhaust System – Some Helpful Hints
Most of the following checks can be made by visual observation and do not require extensive measurements.
If airflow is low in hoods, check:
- Fan rotation (reversed polarity will cause the fan to run backward; a backward-running centrifugal fan delivers only 30-50% of rated flow);
- Fan RPM;
- Slipping belt;
- Clogged or corroded fan wheel and casing;
- Clogged ductwork (high hood static pressure and low air flow may indicate restricted ducts; open clean-out doors and inspect inside ducts);
- Closed dampers in ductwork;
- Clogged collector or air cleaning devices;
- Weather cap too close to discharge stack (a ¾ duct- diameter gap should exist between cap and stack; weather caps are not recommended);
- Poorly designed ductwork (short radius elbows); (branch entries enter main duct at sharp angles); (ductwork diameter too small for the air-flow needed; and
- Lack of make-up air (high negative pressures affect propeller fan system output; lack of supplied make-up air causes high airflow velocities at doors and windows).
If airflow is satisfactory in a hood, but contaminant control is poor, check:
- Crossdrafts (from process air movements); (worker-cooling fans and air-supply systems); (open doors and windows);
- Capture velocity (work operation too far from hood opening);
- Hood enclosure: (door, baffles, or sides may be open or removed); and
- Hood type: (canopy hoods are inappropriate for toxic materials)
Source: https://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_3.html#iii:3_3