Does everyone who goes underground wear a harness so that it's already on should they need rescuing? Or in the 3 minutes, might a rescuer first need to put a harness on the person being rescued?
with due respect you need to do few corrections. 1. Length of the multigas monitor tube is not sufficient to reach the bottom of the confined space. 2. We do not check Oxygen level only, there may be other toxic and flammable gases present e.g. H2S, CO etc. 3. Rescuer hit the SCBA with manhole entrance. SCBA has 4500 psi pressure inside. Hit with the wall are any other object may damage the cylinder and could cause serious injury. 4. You mentioned that oxygen tank, its breathing air "not the oxygen".