MSHA - Code of Federal Regulations - 30 CFR 7.66
30 CFR § 7.66
Output energy test.
(a) Test procedures. The blasting unit shall be tested by
firing into each of the following resistive loads, within a tolerance of
(1) The maximum blasting circuit resistance.
(2) Any resistive load between 3 ohms and the maximum
blasting circuit resistance.
(3) One ohm.
(b) Acceptable performance. (1) The voltage shall be zero at
the firing line terminals 10 milliseconds after operation of the firing
(2) The electric current from the blasting unit shall
(b)(2)(i) Less than 50 milliamperes except during firing of the
(b)(2)(ii) Available only through the firing line
(b)(2)(iii) At least an average of 2 amperes during the first
5 milliseconds following operation of the firing switch.
(b)(2)(iv) Not exceed an average of 100 amperes during the
first 10 milliseconds following operation of the firing switch.