1910.94(c)(6): Velocity and air flow requirements
Key takeaways
- 1910.94(c)(6) is part of OSHA's general industry standards (29 CFR Part 1910, Subpart G).
- Related part: 1910.94(c) Spray finishing operations (30 citations).
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In this article
What this rule covers
29 CFR 1910.94(c)(6) ("Velocity and air flow requirements") is one requirement inside 1910.94 Ventilation, an OSHA general industry standard (Part 1910, Subpart G). It includes 3 sub-paragraphs. The official text below is copied word for word from the Electronic Code of Federal Regulations (eCFR). The numbers, injury cases and training on this page show how OSHA enforces it on real job sites.
Official text
(6) Velocity and air flow requirements.
(i) Except where a spray booth has an adequate air replacement system, the velocity of air into all openings of a spray booth shall be not less than that specified in Table G-10 for the operating conditions specified. An adequate air replacement system is one which introduces replacement air upstream or above the object being sprayed and is so designed that the velocity of air in the booth cross section is not less than that specified in Table G-10 when measured upstream or above the object being sprayed. Open (c)(6)(i)
| Operating conditions for objects completely inside booth | Crossdraft, f.p.m. | Airflow velocities, f.p.m. | |
|---|---|---|---|
| Design | Range | ||
| Electrostatic and automatic airless operation contained in booth without operator | Negligible | 50 large booth | 50-75 |
| 100 small booth | 75-125 | ||
| Air-operated guns, manual or automatic | Up to 50 | 100 large booth | 75-125 |
| 150 small booth | 125-175 | ||
| Air-operated guns, manual or automatic | Up to 100 | 150 large booth | 125-175 |
| 200 small booth | 150-250 | ||
| Notes: | |||
| (1) Attention is invited to the fact that the effectiveness of the spray booth is dependent upon the relationship of the depth of the booth to its height and width. | |||
| (2) Crossdrafts can be eliminated through proper design and such design should be sought. Crossdrafts in excess of 100fpm (feet per minute) should not be permitted. | |||
| (3) Excessive air pressures result in loss of both efficiency and material waste in addition to creating a backlash that may carry overspray and fumes into adjacent work areas. | |||
| (4) Booths should be designed with velocities shown in the column headed “Design.” However, booths operating with velocities shown in the column headed “Range” are in compliance with this standard. | |||
(ii) In addition to the requirements in paragraph (c)(6)(i) of this section the total air volume exhausted through a spray booth shall be such as to dilute solvent vapor to at least 25 percent of the lower explosive limit of the solvent being sprayed. An example of the method of calculating this volume is given below.
To determine the lower explosive limits of the most common solvents used in spray finishing, see Table G-11. Column 1 gives the number of cubic feet of vapor per gallon of solvent and column 2 gives the lower explosive limit (LEL) in percentage by volume of air. Note that the quantity of solvent will be diminished by the quantity of solids and nonflammables contained in the finish.
To determine the volume of air in cubic feet necessary to dilute the vapor from 1 gallon of solvent to 25 percent of the lower explosive limit, apply the following formula:
Dilution volume required per gallon of solvent = 4 (100−LEL) (cubic feet of vapor per gallon) ÷ LEL
Using toluene as the solvent.
(1) LEL of toluene from Table G-11, column 2, is 1.4 percent.
(2) Cubic feet of vapor per gallon from Table G-11, column 1, is 30.4 cubic feet per gallon.
(3) Dilution volume required=
4 (100−1.4) 30.4 ÷ 1.4 = 8,564 cubic feet.
(4) To convert to cubic feet per minute of required ventilation, multiply the dilution volume required per gallon of solvent by the number of gallons of solvent evaporated per minute.
| Solvent | Cubic feet per gallon of vapor of liquid at 70 °F. | Lower explosive limit in percent by volume of air at 70 °F |
|---|---|---|
| Column 1 | Column 2 | |
| Acetone | 44.0 | 2.6 |
| Amyl Acetate (iso) | 21.6 | 1 1.0 |
| Amyl Alcohol (n) | 29.6 | 1.2 |
| Amyl Alcohol (iso) | 29.6 | 1.2 |
| Benzene | 36.8 | 1 1.4 |
| Butyl Acetate (n) | 24.8 | 1.7 |
| Butyl Alcohol (n) | 35.2 | 1.4 |
| Butyl Cellosolve | 24.8 | 1.1 |
| Cellosolve | 33.6 | 1.8 |
| Cellosolve Acetate | 23.2 | 1.7 |
| Cyclohexanone | 31.2 | 1 1.1 |
| 1,1 Dichloroethylene | 42.4 | 5.9 |
| 1,2 Dichloroethylene | 42.4 | 9.7 |
| Ethyl Acetate | 32.8 | 2.5 |
| Ethyl Alcohol | 55.2 | 4.3 |
| Ethyl Lactate | 28.0 | 1 1.5 |
| Methyl Acetate | 40.0 | 3.1 |
| Methyl Alcohol | 80.8 | 7.3 |
| Methyl Cellosolve | 40.8 | 2.5 |
| Methyl Ethyl Ketone | 36.0 | 1.8 |
| Methyl n-Propyl Ketone | 30.4 | 1.5 |
| Naphtha (VM&P) (76° Naphtha) | 22.4 | 0.9 |
| Naphtha (100 °Flash) Safety Solvent—Stoddard Solvent | 23.2 | 1.0 |
| Propyl Acetate (n) | 27.2 | 2.8 |
| Propyl Acetate (iso) | 28.0 | 1.1 |
| Propyl Alcohol (n) | 44.8 | 2.1 |
| Propyl Alcohol (iso) | 44.0 | 2.0 |
| Toluene | 30.4 | 1.4 |
| Turpentine | 20.8 | 0.8 |
| Xylene (o) | 26.4 | 1.0 |
| 1 At 212 °F. | ||
(iii)
(a) When an operator is in a booth downstream from the object being sprayed, an air-supplied respirator or other type of respirator must be used by employees that has been approved by NIOSH under 42 CFR part 84 for the material being sprayed.
(b) Where downdraft booths are provided with doors, such doors shall be closed when spray painting.
Source: eCFR, text current as of 2026-10-15. Read all of 1910.94.
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OSHA interpretation letters
None exist. OSHA has not published a letter of interpretation for 1910.94(c)(6).
Related parts of this rule
- 1910.94(c) Spray finishing operations 30 citations
- 1910.94(c)(2) Location and application 11 citations
- 1910.94(c)(8) Scope
- 1910.94(c)(6)(i)
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About this page
Sources
- 29 CFR 1910.94 (eCFR), text current as of 2026-10-15
- U.S. Department of Labor enforcement data: OSHA inspections, citations and accident records, copied nightly
3-year window. Federal OSHA only; state-plan rules are not counted. Plain-language text is a summary, not legal advice; the official text controls. Black Belt Safety is not part of OSHA or the Department of Labor.