As a consultant, you find yourself in a vast array of work environments. These may include underground utility vaults that have just experienced a “small” fire. Recently, I found myself in just such a scenario, working side by side with a utility worker crew preparing to enter a confined space to conduct a damage assessment. Our project was to evaluate the post-fire atmosphere of the underground street vault prior to the crew entering. It was standard operating procedure to conduct redundant readings from separate entities following this type of event and get agreement of a safe atmosphere prior to entry. Good practice.
The utility crew was onsite first and had their four-gas meter (and forced ventilation) set up. [The four-gas meter is the go-to instrument at a minimum for any confined space atmosphere evaluation. Most are set up for measuring oxygen (%); combustible gas (% of the lower explosive limit); carbon monoxide level (ppm), and the hydrogen sulfide level (ppm).]