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Subchapter 7. General Industry Safety Orders
Group 16. Control of Hazardous Substances
Article 107. Dusts, Fumes, Mists, Vapors and Gases

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§5155. Airborne Contaminants.

(a) Scope and Application.
(1) This section establishes requirements for controlling employee exposure to airborne contaminants and skin contact with those substances which are readily absorbed through the skin and are designated by the “S” notation in Table AC-1 at all places of employment in the state.
(2) When this section references another section for controlling employee exposures to a particular airborne contaminant, the provisions of this section for such substance shall apply only to those places of employment which are exempt from the other standard.
Exception: The provisions for strontium chromate contained in this section shall continue to apply in all workplaces and shall be in addition to the requirements stated in Sections 1532.2, 5206, and 8359.The provisions for strontium chromate contained in this section shall continue to apply in all workplaces and shall be in addition to the requirements stated in Sections 1532.2, 5206, and 8359.
Note: Table AC-1 of this section presents concentration limits for airborne contaminants to which nearly all workers may be exposed daily during a 40-hour workweek for a working lifetime without adverse effect. Because of some variation in individual susceptibility, an occasional worker may suffer discomfort, aggravation of a pre-existing condition, or occupational disease upon exposure to concentrations even below the values specified in these tables. The exposure limits established by this section reflect current medical opinion and industrial hygiene practice, doubts being resolved on the side of safety, and are intended to be used in accordance with good industrial hygiene practice by qualified persons. The division recognizes the need for almost continuous review of these concentration limits and also anticipates the need for including new or additional substances. Harmful exposure to any substances not listed in this section shall be controlled in accordance with section 5141.
(b) Definitions.
Ceiling Limit. The maximum concentration of an airborne contaminant to which an employee may be exposed at any time.
Eight-Hour Time-Weighted Average Concentration (TWA). An employee's exposure, as measured or calculated by the formula in Appendix A, to an airborne contaminant during a workday.
Permissible Exposure Limit (PEL). The maximum permitted 8-hour time-weighted average concentration of an airborne contaminant.
Short Term Exposure Limit (STEL). A 15-minute time-weighted average exposure which is not to be exceeded at any time during a workday even if the 8-hour time-weighted average is below the PEL. An averaging period other than 15 minutes may be specified in the footnotes at the end of Table AC-1.
(c) Exposure Limits.
(1) Permissible Exposure Limits (PELs).
(A) An employee exposure to an airborne contaminant in a workday, expressed as an 8-hour TWA concentration, shall not exceed the PEL specified for the substance in Table AC-1.
(B) When substances have additive health effects as described in section (B) of the Appendix to section 5155, the value of D shall not exceed unity.
(2) Short Term Limits.
(A) Short Term Exposure Limit. An employee exposure to an airborne contaminant, expressed as a 15-minute time-weighted average concentration, shall not exceed the STEL specified for the substance in Table AC-1 at any time during the workday. If another averaging period is indicated in the footnotes to Table AC-1, the time-weighted average exposure over that time period shall not exceed the specified STEL at any time during the workday.
(B) All Other Substances Without a Ceiling Limit. Employee exposure to concentrations above the PEL shall be controlled so as to prevent harmful effects such as narcosis, significant irritation of the eyes, skin or respiratory tract, or chronic or irreversible tissue change.
Note: Such substances are not known to cause adverse effects if the maximum concentration of exposure is limited in accordance with the following guidelines.
PEL Value*
Multiplication Factor
(From Table AC-1)
For Maximum Concentration
0 to 1
>1 to 10
*Use ppm value unless the concentration is only expressed in mg/M3
(3) Ceiling Limits. Employee exposures shall be controlled such that the applicable ceiling limit specified in Table AC-1 for any airborne contaminant is not exceeded at any time.
(d) Skin Notation and Protective Clothing. The substances designated by “S” in the skin notation column of Table AC-1 may be absorbed into the bloodstream through the skin, the mucous membranes and/or the eye, and contribute to the overall exposure. Appropriate protective clothing shall be provided for and used by employees as necessary to prevent skin absorption.
Note: The above requirement does not remove the employer's responsibility to provide appropriate protection from corrosive or skin irritating materials which may not bear the “S” designation.
(e) Workplace Monitoring.
(1) Whenever it is reasonable to suspect that employees may be exposed to concentrations of airborne contaminants in excess of levels permitted in section 5155(c), the employer shall monitor (or cause to have monitored) the work environment so that exposures to employees can be measured or calculated.
(2) When exposures to airborne contaminants are found or are expected to exceed allowable levels, measures to control such harmful exposures shall be instituted in accordance with section 5141.
(3) For the adequate protection of employees, the person supervising, directing or evaluating the monitoring and control methods shall be versed in this standard and shall be competent in industrial hygiene practice.
Note: To facilitate the detection of conditions leading to serious overexposures, the screening of the work environment by any person authorized by the employer, using appropriate measuring devices, is encouraged.
(4) All monitoring results shall be recorded and such records shall be retained in accordance with section 3204.
(f) Medical Surveillance. A medical surveillance program approved by the division may be required to ensure satisfactory maintenance of employee health and to ascertain the effectiveness of the control method(s).

Table AC-1

Appendix to section 5155

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