Staff and volunteers at a joint Gungahlin emergency services building were not exposed to harmful lead dust or diesel particulates, an investigation has found.
But staff will not return to the building until an industrial clean is completed and the site is assessed.
The Gungahlin Joint Emergency Services Centre was cleared out in late February after tests revealed diesel particulate and lead dust contamination.
The Justice and Community Safety Directorate on Thursday briefed staff and unions on the situation, and released an independent report into the contamination.
The investigation found no remediation was required unless the building is to be renovated or demolished.
However, a full industrial clean will be completed to remove diesel contaminants.
"This is not required by WorkSafe ACT, but we know our staff and volunteers have been concerned and we want to reassure them that we are providing a safe work environment," a directorate spokesperson said.
"Staff will not return to the JESC building until we have fully assessed the situation and can ensure that it is safe to do so.
"This investigation has assured us that preventative measures such as exhaust fans, vehicle maintenance and regular industrial cleaning is effective."
The report found there had been a low risk to regular workers in the building and those accessing the ceiling space.
The investigation, conducted by Property Risk Australia, recommended requiring respiratory protective equipment for workers accessing the ceiling cavity.
"No source of lead dust was identified during the investigation, and it is suspected that external atmospheric factors have contributed to a buildup of dust within the ceiling space that exceeds the adopted criteria for lead," the report said.
The investigation found there was no action needed to remove diesel particulates.
The union representing firefighters had called for anyone found responsible for allowing diesel and lead contamination to build up at building to face prosecution for failing to keep workers safe.
Emergency Services Agency Commissioner Wayne Phillips last month said staff had been moved to West Belconnen and Dickson after contamination was found in the Gungahlin Joint Emergency Services Centre.
"The build up of diesel particulates is a very dangerous situation for workers inside a building. We're looking at the cleaning of that. ... I have a passion about reducing emergency service personnel exposure to carcinogens," Mr Phillips said.
ACT Policing officers were temporarily stationed in a command truck outside the joint emergency services centre, but the approach was abandoned after "issues [with the arrangement] could not be satisfactorily resolved".
The arrangement, designed to offer front office services and a location for people meeting bail reporting conditions, left officers with nowhere to shower or change for work, or secure their firearms and accoutrements. Toileting was via a portaloo set up behind crime-scene screens.
