The Occupational Safety and Health Admini- stration’s (OSHA’sNoise standard (29 CFR 1910.95) requires employers to have a hearing conservation program in place if workers are exposed to a time-weighted average (TWA) noise level of 85 decibels (dBA) or higher over an 8-hour work shift.

29 CFR 1910.95(a). 

Protection against the effects of noise exposure shall be provided when the sound levels exceed those shown in Table G-16 when measured on the A scale of a standard sound level meter at slow response. When noise levels are determined by octave band analysis, the equivalent A-weighted sound level may be determined as follows:

Equivalent sound level contours. Octave band sound pressure levels may be converted to the equivalent A-weighted sound level by plotting them on this graph and noting the A-weighted sound level corresponding to the point of highest penetration into the sound level contours. This equivalent A-weighted sound level, which may differ from the actual A-weighted sound level of the noise, is used to determine exposure limits from Table 1.G-16

29 CFR.1910.242(b)

U.S. Department of Labor
Occupational Safety & Health Administration

OSHA Instruction STD 01-13-001 – STD 1-13.1 October 30, 1978 – Reduction of Air Pressure below 30 psi for Cleaning Purposes

February 14, 1972


To: National and Field Offices

SUBJECT: Reduction of Air Pressure Below 30 psi for Cleaning Purposes

Attachment: Acceptable Methods for Complying with 41 CFR 50-204.8 and 29 CFR 1910.242(b)

1. Purpose. To provide guidance and examples of what alternate systems will meet the requirements of this section, and to clarify its intent.

2. Background. A number of inquiries have been received requesting a clarification of the meaning of 1910.242(b) also known as 41 CFR 50-2048 under the Walsh-Healey Act.

3. Interpretation. The phrase “reduce to less than 30 psi” means that the downstream pressure of the air at the nozzle (nozzle pressure) or opening of a gun, pipe, cleaning lance, etc., used for cleaning purposes will remain at a pressure level below 30 psi for all static conditions. The requirements for dynamic flow are such that in the case when dead ending occurs a static pressure at the main orifice shall not exceed 30 psi. This requirement is necessary in order to prevent a back pressure buildup in case the nozzle is obstructed or dead ended. See enclosure (1) for two acceptable methods of meeting this requirement. Also, there is no intent to restrict the diameter of the nozzle orifice or the volume (CFM) flowing from it.

“Effective chip guarding” means any method or equipment which will prevent a chip or particle (of whatever size) from being blown into the eyes or unbroken skin of the operator or other workers. Effective chip guarding may be separate from the air nozzle as in the case where screens or barriers are used. The use of protective cone air nozzles are acceptable in general for protection of the operator but barriers, baffles or screens may be required to protect other workers if they are exposed to flying chips or particles.

4. Action. Inquiries about subject section should be handled in accordance with this instruction.

5. Effective Date. This instruction is effective immediately, and will remain in effect until canceled or superseded.

Director, of Program Operations

DISTRIBUTION: National Office Field

A/SEC. (3) Regional Administrators (6) Dep. A/Sec (2) Area/District Offices (3) Spec. Asst. (1) Training Institute (1) Directors (3) RAO (2) SOL (1) Professional Staff (1) BLS (1) Review Commission (6)

For Attachment see Printed Copy Acceptable Methods For Complying With 41 CFR 50-204.8 and 29 CFR 1910.242(b) Use of Compressed Air

See OSHA Standards Attachment