30 CFR §7.66

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