California Code of Regulations
Title 8 - Industrial Relations
Division 1 - Department of Industrial Relations
Chapter 4 - Division of Industrial Safety
Subchapter 7 - General Industry Safety Orders
Group 18 - Explosive Materials
Article 116 - Handling and Use of Explosive Materials in Blasting Operations
Section 5291 - Firing of Explosive Materials (Blasting Operations)

(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:

(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:

(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.