Date Time All work involving gas must be done by book A gas explosion in Christchurch which left six people seriously injured and several properties uninhabitable serves as a warning to all gasfitters, says WorkSafe. All work with gas must be done by the book – because when things go wrong, the consequences can be grave. In July 2019, certifying gasfitter Gregory John Smith was repairing a fireplace at a home in Christchurch. As part of the repairs he removed a gas valve, which is used to control the flow of gas. He advised he would return the next day to complete the repairs.