A study released Tuesday by the largest patient-safety non-profit in the U.S. found that up to 70% of KN95 masks do not meet the U.S. standards for effectiveness in combating the spread of COVID-19. The KN95 masks are mostly made in China and are being used by some healthcare providers as an alternative to the U.S.-made N95 masks. 

ECRI tested 200 KN95 masks and found that 60%-70% of the masks fail to filter out 95% of aerosol particulates.

The ECRI study concluded that most KN95 masks “do not meet U.S. standards for effectiveness, raising the risk of contracting COVID-19 for care providers and patients at hospitals and other healthcare organizations.”

“Because of the dire situation, U.S. hospitals bought hundreds of thousands of masks produced in China over the past six months, and we’re finding that many aren’t safe and effective against the spread of COVID-19,” ECRI president Marcus Schabacker said in a statement.

“Using masks that don’t meet U.S. standards puts patients and frontline healthcare workers at risk of infection. As ECRI research shows, we strongly recommend that healthcare providers going forward do more due diligence before purchasing masks that aren’t made or certified in America.”

The U.S continues to face a shortage of N95 masks designed for one-time use. The shortages began in mid-March, when the COVID-19 pandemic first hit New York City. 

President Donald Trump invoked the Defense Production Act to speed production of ventilators, but he has not used much of his authority to force production of masks and other types of personal protective equipment (PPE). 

A recent survey of more than 21,000 nurses conducted by the American Nurses Association found that a third of respondents are either short or without N95 masks. Almost 60% said they are reusing PPE for five or more days.

Masks will be even more needed in the coming months, as public health experts warn of a second wave of the virus. On Tuesday, the U.S. death toll from the virus surpassed 200,000.