The fridge that exploded smashing windows and causing serious damage to a Greerton home is being held for further investigation.

The 1.15am blast on Wednesday blew out the door of the fridge and blasted through most of the Scott Street unit's windows.

The fridge that exploded in a Gate Pa flat has been impounded so explosives experts from Wellington can investigate.

The two residents, JD Smith and Paul Collinson, who were sleeping at the time, were unhurt.

Fire investigators have since failed to find a cause for the explosion and fire safety officer Ken McKeagg says the fridge will now be examined by explosives experts from Wellington.

'The Ministry of Commerce just wanted to hold onto it to see if was actually something these guys had stored in the fridge, which we don't think it is, or if the refrigerant has been replaced with something else,” says Ken.

The fridge was purchased from a Salvation Army store and is about 20-years-old.

Former non-flamable refrigerant gases like Freon are now considered greenhouse gases and are being replaced under the Montreal protocol.

'I think all CFCs had to be replaced by end of 2012, replaced with a safe gas,” says Ken. 'Unfortunately the safe gas is a derivative of GNG/LPG. It's ozone friendly. The only downside is it is highly flammable.

'The fridge is very old and they wanted to see if it has been refilled with the new hydrocarbons, then we know it's not a product failure. Somebody's done a shortcut, a little bit like what happened at Tamahere.

'Tamahere had a refrigerant system designed for one gas and they put a different gas in it, this is what we are checking with this one, that's all.”

The Tamahere Icepak Coolstore exploded in flames in April 2008, while firefighters were in the plant room.

The blast killed senior station officer Derek Lovell and seriously injured seven other firefighters. It was caused by leaking flammable refrigerant gas being ignited by an electrical spark.

Ken says the danger of putting new gas in old fridges is the Greengas is dryer, it can dry out seals, causing leaks.

The men from the ministry are expected to examine the fridge in the next week or two.