Those that have managed to get a respirator could either use to mine or simply stand around and rent it out to tourists wanting to go down and have a look. It turns out that it's more profitable to simply rent the respirators than to actually mine. Hence, the prevalence of the miners w/o a mask. (not only is it expensive, masks like these just don't exist in that area - they're bartered for or given by tourists that feel bad for them). I was asked to 'give' my mask to one of these guys - I laughed at him. I'd much prefer to give it to an actual miner who needs it.