The state health department said this week that hundreds of thousands of KN95 masks that have been distributed across New York state in recent weeks are “in question as to their efficacy.”

New York has shipped millions of KN95 masks to New York counties amid the rise of the Omicron variant and the state’s mandate to use masks in indoor public spaces, which took effect in December and lasted through February 1.

Face shields are designed to provide a high level of protection against COVID-19, due to the mask’s tight fit and thin fibers of the material that can block small airborne particles.

N95 masks, certified to US standards (KN95 masks are out-of-state approved), are often used in healthcare settings, along with surgical masks, which also provide a higher level of protection than cloth masks.

But 250,000 of about 5 million KN95 masks distributed statewide so far, about 5%, have been recalled since questions about their quality emerged.

“The state has distributed millions of masks to counties for schools, libraries and other public facilities, a small portion of which are the face masks involved,” Health Department spokeswoman Erin Silk said in a statement this week. “Affected counties have been contacted and asked to remove the masks in question and new masks will be shipped for immediate replacement.”

New York does not require or recommend that residents wear a specific type of mask, other than one that fits the face well.

Initially, the Centers for Disease Control and Prevention discouraged residents from wearing N95 or KN95 masks for fear of running out of supplies for health care workers, but the agency is now considering recommending such masks amid the alternative. omicron is highly contagious, according to the Washington Post.

The agency analyzes standards for N95 masks on its website, noting that about 60% of KN95s in the country are fake.

About 180,000 of the masks involved in New York went to Monroe County, out of a total of 337,620 KN95 masks distributed in that county. About 30,000 went to Madison County, between Syracuse and Utica, and another 36,000 to Niagara County, in western New York.

The masks are manufactured by Yixian Songlin Bioengineering Co., Ltd. It is supplied in clear plastic packages of 25 units each.

“We are aware of concerns about the quality of some of the KN95 masks that the State of New York recently purchased and distributed to Monroe County,” county spokeswoman Megan McDermott said in a statement. “Once Monroe County receives additional masks, we will work to replace masks for those who were unable to use them.”

In Madison County, the original masks have been delivered to schools and city offices for distribution, according to a county statement Thursday. It is not clear when the new masks will arrive, but when they do arrive, they will be distributed in the same places, the statement said.