Manufacturers' claims about air purifiers on sale in Hong Kong overstate their cleaning ability by as much as 17 times, tests by the Consumer Council found.
None of the 10 machines tested by the council could clean as big an area as stated, while some also had inadequate insulation, posing a risk of electricity leakage.
The purifiers included seven large models and three small ones ranging in price from HK$629 to HK$4,000.
The exaggeration of the cleaning area was greatest in the smaller models. One purifier made by Giabo claimed it could clean an area of 10 square metres, but in reality could handle just 0.6 of a square metre.
The vice-chairman of the council's publicity and community relations committee, Professor Ron Hui Shu-yuen, said consumers should look at the clean air delivery rate when they buy air purifiers to assess their efficiency. The bigger the number, the better they can clean, he said.
The council found electric insulation in four models unsatisfactory and warned of electric leakage. In others, heat and flame retardant capabilities were also inadequate.