A form of rebreather that filters dust and harmful chemicals to an extent.
Mechanics: Makes you immune to gas based poisons and other gas based effects for a number of rounds depending on the severity of the effect. Cleans itself once per day.

Strenght enhancers (untyped bonus), only usable in 1 round bursts with cooldown. Originally used to allow the workers to lift or maneuver heavy objects in there.

Flashlights of some kind.

Emergency Noise Creator: Consumable
Emits a deafening noise (Fort save negates) in a radius of 10ft.
Original Use: Signal of someone being in trouble as sound should carry well in a mine.

Each worker has a watch. These watches are all synchronized and never stray from one another as they were made to for always having workers know when to expect explosions etc.