But the TFS says Forexpan-S - a Class A firefighting foam utilised in bush firefighting - is perfectly safe.

United Firefighters Union Tasmania branch industrial organiser Stephen McCallum said firefighters at the Rocherlea Fire Station had noticed a container of the foam on the back of a truck over the weekend.

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Mr McCallum said firefighters interstate had reported a number of symptoms after using Forexpan-S, including respiratory issues, skin conditions and "potentially even birth defects".

"Essentially, we'd like the TFS to take a precautionary approach where [if] there's not enough science to say clearly if it is or isn't toxic to firefighters or causing these conditions, then they need to switch to an alternative foam until there is significant evidence on the matter," he said.

"Members have advised that [Forexpan-S is] used at a number of stations, particularly at volunteer firefighter stations. The foam is predominantly used for bush firefighting, so our rural fire stations are more likely to have it in stock."

Mr McCallum said his members had "completely lost faith in TFS to protect their health and safety".

"There's a long history of health and safety concerns being raised and not properly addressed," he said.

The UFU raised concerns about the use of Forexpan-S in Australia as far back as 1997, when career firefighters working for the Country Fire Authority in Victoria began to worry about what they perceived to be possible health effects associated with the substance.

The CFA stopped the regular use of the foam due to these concerns, a spokesperson said.

"To maintain consistency, CFA transitioned both career and volunteer firefighters to a different firefighting foam," the spokesperson said.

"CFA investigated Forexpan-S at the time and did not believe it posed a health risk.

"Forexpan-S continues to be used widely around the world and by other Australian fire services.

"Due to a national supply shortage of our preferred foam in 2013, CFA volunteers used Forexpan-S foam for a time before reverting back to the preferred foam."

The TFS said it had updated its procurement process and now endorsed the use of Phos-Check WD881A as its primary Class A foam concentrate.

"Forexpan-S continues to be approved for use in ground firefighting operations until legacy supplies have been exhausted," a TFS spokesperson said.

"TFS was not aware of the concerns of any TFS firefighters about this product prior to it being raised with the media."

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