We use a Topcon total station and a Carlson data collector daily in a coal mine and have never been questioned by inspectors. We do also carry a multi gas monitor.
We do have personal H2S monitors, and if available will have the multi gas meter with us as well.
That's a great point to address as well Richard.
I appreciate all input from fellow professionals. I have found that even though there is no "intrinsically safe" survey TS, there seems to be a lot of variation between clients about practices and methods. My ex-employer does some work for a large refinery and they have to have a sniffer with them at all times with the TS. I will have to get further details from the client. Again thank you!!
German Mining Theodolite - I believe K&E offered this in their catalog many years ago.
http://www.breithaupt.de/en/products/theodolites/mining-suspension-theodolite/temin/
Electric spark can be source of ignition for methane gas in a mine or even coal dust if enough is suspended in the air. Same thing can happen in a flour mill or grain elevator building if the amount of dust in the air is high enough. Mill or elevator explosions can be powerful enough to punch large holes in reinforced concrete structures and kill. I heard about a comedian who included in his act throwing powdered creamer in the air and then igniting creating a mini explosion on stage.
During my time working in the surveying product industry, company explored what it would take to get intrinsically safe certification for an add-on EDM to use in coal mining. My recollection is the test was to put the product in an explosion proof chamber fill with gas until an explosion happened. Concentration of gas at time of explosion determined safety level. So you could blow up several products trying to reach certification. Like highway safety crash tests. Sacrifice the product to see how safe it is. Best way was to design the product from the start to achieve it. Trying to retrofit existing product much harder.