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California’s health department on Thursday started recommending that residents “double mask” to better protect from the spread of the coronavirus.

While the state doesn’t require wearing two masks over each other, Gov. Gavin Newsom said people who use cloth face coverings are encouraged to do so.

“We are encouraging people basically to double down on mask wearing, particularly in light of all of what I would argue is bad information coming from at least four states in this country,” Newsom said. “We will not be walking down their path. We’re mindful of your health and our future.”

Newsom’s remarks come after Mississippi and Texas governors ended their mask mandates.

“The positivity rate in those states is substantially higher than even here in the state of California,” Newsom said. “And yet, we still feel very, very strongly — as we begin to loosen things up and reopen our economy — that mask wearing is becoming now more essential as we transition to herd immunity and broad access to vaccines.”

The U.S. Centers for Disease Control and Prevention last month released research saying that layering a cloth face covering over a surgical mask increases protection from respiratory droplets and aerosols.

They also found that knotting the mask’s ear loops and then tucking in and flattening the extra material close to the face also provides more protection.

In lab tests using dummies, exposure to aerosols decreased by about 95% when both wore rightly fitted masks, including a cloth mask over a surgical one and medical masks with knotted ear loops, according to the CDC.

Some Americans had already started wearing two masks, and experts think that’s partly because of worries over the new coronavirus variants found to spread more easily, the Associated Press reports.

Layering more than two masks is not recommended because it could make it difficult to breathe. It’s also not recommended to wear two medical masks, or to wear a medical mask on top of a KN95 or an N95.

Here’s how California’s heath department ranks the effectiveness of different masks: