One-quarter of air purifiers sold on the domestic market are substandard, an inspection by China's top quality authority showed.

The inspection, conducted in the first half of this year, found 15 of the 61 batches of products were substandard, according to the General Administration of Quality Supervision, Inspection and Quarantine.

This is the first time that the administration has organized a national quality inspection aimed at air purifiers, and the inspection covered most well-known air purifier brands available in China, said Zhang Wenbing, chief for quality supervision at the administration.

The inspection covered nearly 20 percent of China's air purifier producers, and of the models by big enterprises, 90 percent were up to standard, much higher than average, according to the administration.

No products by big brands such as Honeywell, Samsung and Midea were found to be substandard.

However, purifiers made by Chinese firms Guangdong Jingba Technology Co and Shanghai Xinsong Electronics Co were found to be substandard, due to respective issues of failing to remove methanol and failing noise standards.

"Results of the inspection can provide the basis for consumers to choose air purifiers," said Song Guangsheng, director of the National Quality Supervision and Inspection Center for Indoor Environment and Environmental Products.

With increasing demand for purifiers in recent years, the number of producers has also risen, but many purifiers on the market may not work as well as advertised, he said.

"Many air purifier brands claim to be able to remove methanol, but in fact, few of them are able to do so," Song said.

In the first half of the year, 4.5 million air purifiers were sold in China, 58 percent more than the same period last year, according to media reports.

Zhang Xiao, an inspector at the National Quality Inspection Center for Household Electrical Appliances, said China has strict quality standards for air purifiers, and some key indexes include noise level, capacity to remove pollutants and purifiers' toxic emissions.