Nine people were killed and 33 injured in the explosion in 2004
Corroded gas pipes needed to be replaced at a Glasgow factory where a fatal explosion killed nine people and injured 33, an inquiry has heard.
Gas engineering expert, Gary Tomlin, has been giving evidence at the second phase of a public inquiry into the blast at ICL plastics on 11 May 2004.
The inquiry, at the Community Central Hall in Maryhill, is being chaired by senior Scottish judge Lord Gill.
Mr Tomlin has carried out research into ageing underground pipe work.
He did the work on behalf of Calor, following a domestic gas explosion in November 2006.
Five hundred installations were examined over a 16-month period, the inquiry heard.
Different pipe materials, soils and pressures were assessed as part of the investigation.
In most cases the section of pipe that corrodes is the metal "riser" pipe that leaves the ground and feeds into the building it supplies, Mr Tomlin said.
The inquiry was told that once a hole appears, an average of 25% of the gas will "migrate" into the building.
The leaking LPG (liquefied petroleum gas) then mixes with the air inside the premises to form a flammable mixture.
When this is ignited it causes an explosion.
Summarising his report, the gas expert said more research was needed and more funding required to help small businesses do the necessary exploratory or replacement work.
He said: "The key factor that needs to take place is the replacement of any corroded pipe."
Factory operators ICL Plastics and ICL Tech were fined £400, 000 by the courts after admitting health and safety breaches last year.
The inquiry has heard previously how metal pipe work installed by the company in 1969 was not examined for corrosion, despite concerns raised by the Health and Safety Executive in the 1980s.
The condition of the underground pipe also went unchecked during the installation of a new LPG tank in 1998.
When the second phase of the inquiry is complete Lord Gill will make recommendations to ministers aimed at helping prevent a similar tragedy.