Japan's Daikin Industries Ltd, the world's No. 2 air conditioner maker, said on Tuesday its air purifier can stop the H1N1 flu virus from spreading.
But a Japanese Health Ministry official said there were uncertainties about the machine, such as whether it could be effective in large public rooms.
Daikin said a joint study with Vietnam's National Institute of Hygiene and Epidemiology had shown that the virus, spreading around the world in a flu pandemic, was no longer contagious after being exposed to its air purifier for four hours.
High-speed plasma electrons generated in the air purifier break down H1N1, other viruses and bacteria to nitrogen, oxygen and water, said Daikin, which developed the technology in 2004.
Daikin this month launched its latest air purifier using the technology, a model which it said is 1.5 times more powerful than its previous versions.
The new H1N1 strain of flu, declared a pandemic in June, could eventually infect one-third of the world's population, or 2 billion people, according to the World Health Organization.
The Health Ministry official said: "Such a machine may function appropriately under certain conditions like in a small room, but may not in places like large gymnasiums, where hundreds of people gather."
The official asked not to be identified because he was not in a position to talk publicly.
Rival Sharp Corp uses similar technology for its air purifiers but has yet to verify its effectiveness on the virus, a Sharp spokesman said.