ACT work safety commissioner Greg Jones said early investigations into the incident indicated that an acetylene gas bottle had leaked into a compartment at the back of the ute.

Mr Jones said an ignition source then caused the explosion, which happened in the car park of St Clare of Assisi Primary School in Conder about 4.55pm on Thursday.

Bystanders rushed to help the 51-year-old father, who had just arrived to collect his child from an after-school care program.

The man, described by school principal Matthew Egan-Richards as "a down-to-earth, good bloke", died in hospital later that night.

The incident, which police are not treating as suspicious, prompted WorkSafe ACT to issue a reminder on Monday about how to store and transport gas cylinders safely.

Mr Jones said while flammable gas cylinders were most commonly transported by tradespeople for jobs like refrigeration, welding and gas fitting, residents often took their LPG cylinders to have them swapped or refilled.

“If there is a leak of gas, then any ignition source - often the vehicle’s electrical system - it can cause a significant explosion,” Mr Jones said.

Mr Jones said gas cylinders must be secured in an upright position, valves must be tightly closed and the regulator, hoses and torch disconnected.

He said it was crucial to make sure cylinders were not struck by other objects like loose tools during transport, that there was no leakage around the main valve test area, and that there was a dry powder fire extinguisher in the vehicle.

Gas cylinders must not be carried in the passenger compartment of any vehicle, and good ventilation is essential.

“If cylinders must be carried in closed areas of vehicles, a storage cabinet with outlets in the base of the cabinet, vented outside the vehicle, must be used,” he said.

Acetylene is a fuel gas which, when combined with oxygen, is generally used for welding, cutting, localised heating and flame hardening.