There have been many fires and explosions in our industry over the years due to ignition during spark-producing Hot Work. The May 2020 Beacon covered the fatal consequences from one such event. One element of preparing for Hot Work is to check for – and prevent – the presence of combustible materials and/or flammable vapors “within 35 ft (10.7m)”.
(* The recommended distances from both US OSHA and the National Fire Protection Assoc.(NFPA)).
Many companies check for flammable vapors at all places where the sparks from the hot work could be expected to bounce. The diagram shows some locations to be checked. LFL gas detector readings need to check around the location of the hot work itself, as well as every place around and below where the hot particles could bounce. This includes using a probe (or sampling hose) to check inside open process pipes or inside sumps and process drains such as points 5-9.
Test in ALL the places where flammable vapors could be ignited !