Here’s a particularly interesting “enclosed/confined space entry” incident that sort of wasn’t, from the Step Change In Safety Website. It highlights an often over-looked hazard – lighter than air gases coming out of a tank:
“While assisting with pre-entry checks prior to entering a tank to carry out quarterly maintenance checks. (The) I(njured) P(erson) lost consciousness and collapsed on deck.
The IP lifted the manhole cover to gain access to the tank for the purpose of air sampling as part of their procedure prior to entering the tank to carry out quarterly maintenance. the IP was working next to his supervisor who began to lower gas sampling equipment into the tank. Within 1 minute of the tank entry cover being opened, while the sampling equipment was approximately 3 metres into the 6 metre deep tank, the gas sensor alarm activated and the IP, who was still outside the tank, lost consciousness. The IP subsequently recovered fully with no apparent residual effects