While I agree with most of Darren’s points I don’t necessarily agree with the reference to working in a fire investigation where “hazards such as holes in floors or areas with compromised building integrity” are present.
If the building is not safe to be in, we should not be entering, period.
Having said that, we quite often will work a fire investigation where there may be some breaches of floors, walls and ceilings, as long as it is safe to do so. But who determines if it is safe for us when we are talking about structural integrity, stability etc.?
I don’t think any of us should ever work alone when conducting a fire investigation, it is still a fire scene, and you won’t find any suppression personnel working alone in a fire scene, why would the investigator be any different?