Tomasz Kupiecki to steve
Your site is very interesting, it`s a good job. I`m Tom, sewer worker from Warsaw, Poland. Photos of London sewers were so familiar- we`ve got sewer net projected by Wiliam Lindley about 1880`s.
I wanna warn you- sewer can be a deadly trap, because of poisonus gases, poor oxygene atmosphere, explosive gases, fast rising level of water, so please, be very, very carefull.
For example I was a victim of explosive gases, in Poland work is still „in oldschool style”- rubber waders, coats, gas masks, tripods from communism era, etc. So- I put my black rubber chest waders and went to manhole. I wade about 30 meters from there in knee deep sludge, to check condition of sewer line (high about 1,9m, wide aobut 3m)... So I was wading, and suddenly I heard somethig like thunderclap, and a mighty force thrown me back, to the manhole. I feel very high temperature, I was knocked down and all covered by sewer sludge... Waders were filled by this... I was trying to keep head above it... My co-workers on the surface were yeling: Tom what is it? I babbled: for God`s sake, pull me out from here, and I fainted. The cause of explosion was someones fag putted to the manhole... Before I was taken to hospital, rescuers had to clean me and remove from me waders filled sludge... In hospital I was all in gypsum costume about half year.
So, please- be very, very carefull.
Best wishes, and sorry for my English, Tom from Warsaw.
I emailed him back and mentioned that I usually carry a gas meter that checks for explosive/flammable gases as well as for hydrogen sulfide and carbon monoxide, but that I don't currently have a working oxygen meter. He sent this diagram and explanation for helping avoid low-oxygen atmospheres: