The government's utility technical regulatory team has been raising its concerns about the internally-installed gas meters in apartment buildings and commercial premises with ActewAGL since at least 2013, primarily with those installed before July 2014 in domestic settings.

While the regulator has not audited the meter installations in the residential buildings, an audit of 17 similar meters installed in commercial settings in 2013-14 found all those inspected "failed to meet 'fit for purpose' requirements of the relevant technical standards".

That audit prompted a wider investigation at the time. The second audit of 157-odd meters in commercial buildings found 68 per cent were also non-compliant.

Despite the findings of the commercial audit, ActewAGL Distribution, now EvoEnergy, has also not historically included such gas meter installations in its annual maintenance and inspection program.

While the large meters are usually installed outside buildings to ensure easy access to them for inspectors and emergency services crews, a series of the regulator's annual report shows those installed indoors could pose a serious risk to apartment dwellers in the event the meter sprung a leak.

It was only the latest in the team's annual reports back to at least 2013-14 that have raised concerns about the risks posed by the indoor meters, primarily due to a lack of ventilation and emergency services access and the ability to isolate the gas supply in the event of a leak.

"The adequacy of apartment ventilation, first response access and ability to isolate the gas supply for these installations remains of concern to [regulators]," the latest report shows.

"[We are] concerned that the current operating regime may, in the event of an internal gas meter set fault, expose occupants of an apartment to gas escaping into occupied areas within the service life of the installation."

A spokeswoman for the regulator said in a statement it had no concerns the internal domestic meter sets were any "more prone to faults" than other sets, and acknowledged that odorant added to the gas would help "leak detection in the event of a fault".

The regulator's concerns last year led it to commission an independent investigation of the 80 such installations in Canberra medium density high-rise apartment buildings, which has been completed, and supplied to EvoEnergy.

But the government has refused to publicly release the investigation report or detail any of its findings or recommendations, after questions about the matter posed on Friday.

The regulator's 2013-14 annual report also showed EvoEnergy failed to provide "documented procedures and processes to demonstrate safe installation of new gas metering equipment for dometic customers in medium density high rise apartments" for three years to 2012-13.

The meter sets have a 15-year serviceable life, but EvoEnergy's annual gas meter maintenance program only requires larger capacity installations, those with more than than 10 cubic metre an hour capacity, to be periodically maintained or inspected.

"[The regulator] has concerns with this approach for gas meter set installations located within medium density high rise apartments," the latest report shows.

"This practice leaves the majority of gas meter set installations not scheduled for any form of maintenance or inspection whilst in service."

It is understood there have not been any actual leaks from those meter installations in residential apartment buildings, and the meters met the relevant codes at the time of installation, though the risk remains.

The latest report also highlighted that while EvoEnergy had, twice in the previous two years, promised to "confirm the appropriateness" of its maintenance program for all gas meter set installations, through independent formal safety assessments, it had not done so.

"Such formal safety assessments and final reports [which were planned to be completed in the previous reporting period] remain outstanding," the report reads.

"[The regulator] continues to seek resolution of this safety concern with [EvoEnergy]."

The regulator's spokeswoman also said EvoEnergy had recently begun a new inspection program to confirm the safety of the domestic gas meter sets, a program that would "run until the end of the year", though it is unclear why it had not done so earlier.

"If Evoenergy finds any installations that require remedial attention, it will undertake a program to rectify these installations," she said.

An EvoEnergy spokeswoman said there had not been any report of safety-related issues to date.

"Internal gas meters have been installed for over 15 years in ACT," she said.