This information is provided free of charge by the Department of Industrial Relations from its web site at These regulations are for the convenience of the user and no representation or warranty is made that the information is current or accurate. See full disclaimer at

Subchapter 7. General Industry Safety Orders
Group 18. Explosives and Pyrotechnics
Article 116. Handling and Use of Explosives--Blasting Operations

Return to index
New query
§5291. Firing of Explosives.

(a) The licensed blaster-in-charge shall fix the time of blasting.

(b) Blasts are not to be fired without a warning signal/procedure. The signals, which may be given by a siren, air horn, whistle or other device, shall be loud enough to be heard clearly in areas that could possibly be affected by the blast or flyrock from the blast. In addition, blasts are not to be fired until the licensed blaster-in-charge verifies the following:

(1) All surplus explosive materials are in a safe place,

(2) All security personnel at the blast area are in the proper location, and

(3) All personnel are either outside of the blast area or under sufficient cover.

(c) Precautions, such as the following, shall be taken to prevent unauthorized entry into the blast area: warning signs, barricades, or flaggers when necessary.

(d) Warning signals shall be given by the use of a compressed air whistle, a horn, lights or equivalent means, such as flaggers or voice warning and shall be clearly audible at the most distant point in the blast area. Where other than flagger or other visible method or voice warning is used, the following signals are recommended:

5 minutes prior to the blast
A 1-minute series of long audible signals
1 minute prior to the blast
A series of short audible signals
Following inspection of the blast area
A prolonged audible signal

(e) The type of warning signal or method shall be posted at one or more conspicuous locations and all employees shall be made familiar with the signals and instructed accordingly.

(f) The “ALL CLEAR” signal shall not be given until the licensed blaster has made a thorough, visual inspection of the blast area for misfires. In the event of a misfire, the requirements of Section 5293 shall be complied with before the “ALL CLEAR” signal is given.

(g) Warning signs, indicating a blast area, shall be maintained at all approaches to the blast area. The warning sign lettering shall not be less than 4 inches in height on a contrasting background.

(h) Whenever blasting is being conducted in the area immediately adjacent to gas pipelines, flammable liquid gas pipelines, electric, water, fire alarm, telephone, telegraph, and steam utilities, the licensed blaster shall notify the appropriate representatives of such pipelines or utilities at least 24 hours in advance of blasting, specifying the location and intended time of such blasting. Verbal notice shall be confirmed with written notice before the blast. In an emergency this time limit may be waived.

(i) Employees shall be prohibited from entering the blast area after blasting until any toxic vapor/fumes, dust and gases have been reduced to safe limits.

(j) After blasting, the blasting crew shall wait at least 5 minutes before returning to the point of blasting.

(k) For underground blasting, no one shall enter the place where primary blasting has been done for at least 15 minutes.

Note: Authority cited: Section 142.3, Labor Code. Reference: Section 142.3, Labor Code.


1. Amendment of subsection (a) and new subsection (e) filed 10-17-75; effective thirtieth day thereafter (Register 75, No. 42).

2. Amendment of section heading, section and Note filed 7-11-2003; operative 8-10-2003 (Register 2003, No. 28).

3. Amendment of subsection (b) and new subsections (b)(1)-(3) filed 2-1-2011; operative 3-3-2011 (Register 2011, No. 5).

Go BackGo Back to Article 116 Table of Contents