The Christchurch gas explosion could have a lasting impact on New Zealand's gas industry.

Five people remain in hospital following Friday's blast at a home in Northwood, including one in a critical condition.

It's unclear exactly what caused the explosion.

Gas and Plumbing Limited owner Wayne Ustace told Mike Hosking the country has seen nothing like it before.

"It'll be ground-breaking for all of the industry. No one will know where to go or what to do because it's never happened. It'll be very spooky for a lot of people in the industry."

The cause of the explosion remains unclear, but Ustace says the message to other households is simple.

"Sometimes there's that typical Kiwi attitude of 'she'll be alright, I've smelt that for a while'. If you smell it, do something about it, don't hesitate."

He says gas users shouldn't be alarmed, but if people smell gas our notice anything out of the ordinary, they should take action.

"Gas is safer probably than fuel, but like anything you've got to do your maintenance and you've got to look after your appliances."