Never heard of it, but I know there is a three-person interlocking blasting system in low-gas mines.

The three people in the "three-person chain blasting" refer to the blaster, the tile inspector and the shift leader of the construction unit.

The gunfire officer holds a warning sign, the tile inspector holds a firecracker sign, and the shift monitor holds a firemanship order sign.

The operation procedure of the three-person chain blasting is: before shooting, the blaster will hand the warning sign to the shift leader of the construction unit. After receiving the warning sign, the shift leader will check the roof and support conditions. After inspection, they are correct. After sending someone to set up a warning sign, you can hand over the firecracking order sign you carry to the tile inspector. After the tile inspector checks that the gas and coal dust are qualified, and there are no unsafe hazards in and around the working surface, he will hand over the firecracking order sign he carries. Hand it over to the gunman, who will sound the gun whistle to fire off the gun. After the blast is fired, the blasters, tile inspectors, and shift monitors must jointly inspect the blasting site. If the ventilation, gas, coal dust, etc. are in compliance with the "Procedures", the blasting effect has achieved the expected purpose, and the roof and support are in good condition. The cards must be returned to their original owners. Otherwise, they must be dealt with immediately. After the processing is completed, the three cards can be returned to their original owners, completing a "three-person interlocking shooting" cycle.

Warning signs, firefighting signs, and firefighting order signs are uniformly ordered by the construction unit. A set of three is issued to the firefighting personnel, tile inspectors, and shift monitors of each relevant unit for safekeeping and use. Firecrackers can only be played between the specified three people, and substitution by others is strictly prohibited. You can only fire one cannon once you change the cards, and it is strictly forbidden to fire the cannons multiple times in a row once you change the cards.

It is strictly prohibited to operate according to the "three-person chain blasting" procedure. After the card replacement, all three people must sign on the record card carried by the blaster for reference. The signing must be done in a safe place outside the cordon, and only after the signing procedures are completed can the gunfire crew whistle and fire off the gunfire.