Heading into the Monday start of Chinese New Year, when markets and businesses close for a week, smartphone startup Xiaomi is hoping to avoid any more criticism.

Its strategy for more than a year has been to use its strong smartphone brand in China, where it ranked first in market share last year, to sell a range of home gadgets under the Xiaomi banner, from a smart TV to fitness band to air filter. Over the past week, the last offering, air filters, has been creating headaches.

The popular devices, which at $140 sell for a fraction of the price of other air filters used inside homes across Chinese cities to combat the notoriously noxious air, are no longer available on the country’s top online shopping sites, Alibaba’s Tmall and JD.com. The listings now product error messages or a note saying they’ve been removed, as Chinese news site Sina.com first reported. It’s as if GoPro suddenly pulled its cameras from Amazon.

The reason may be a failed government inspection in January. The Shanghai Quality and Technical Supervision department said Xiaomi’s air filter had a “grave quality problem” with the amount of clean air it produced, specifically with a measurement known as the clean air delivery rate (CADR).

“CADR can be regarded as the most important and significant indicator to evaluate an air purifier’s quality,” says Zhao Bin, a professor at Tsinghua University’s department of building science who focuses on indoor air pollution. “If an air purifier’s CADR has a ‘grave quality problem,’ it would definitely fail to reduce pollutants effectively.”

Xiaomi’s response is that the rate used by the Shanghai inspector, which was not disclosed, was a recommended standard, not a compulsory standard. Xiaomi also posted an earlier test completed before the air filter was first sold in December 2014 that showed the clean air delivery rate (CADR) at 409 cubic meters per hour and 406.6 cubic meters per hour, rates that compare favorably to other brands.

Nevertheless, either Xiaomi or Xiaomi’s partner Zhimi, which manufacturers the air filter, is pulling it from resellers until the tests are sorted out. A Xiaomi spokeswoman didn’t respond to a request for comment Friday.

It is an undeniable blow for Xiaomi, which has staked its reputation on devices made by others.

Hundreds of critical comments piled up on Chinese social media in response to the Shanghai test, some referencing earlier problems with the air filter. Late last year, stories appeared first on social media, then in the Chinese state press, accusing Xiaomi of fraud. Users who hadn’t first removed the plastic covering from the filter said the Xiaomi air sensor displayed decreasing rates of inside air pollution.

The latest news comes after Xiaomi failed to reach its smartphone sales target last year of 80 million sold and analysts are questioning the startup’s $45 billion valuation.

Xiaomi must be ready for the week-long holiday.

With reporting by Tian Chenwei.