Residents in the Southland and across the country have been urged for nearly a year to wear a mask to prevent the spread of COVID- 19, but federal health authorities today said people should consider wearing two.

The U.S. Centers for Disease Control and Prevention released a study that again backed the effectiveness of wearing a face covering to block respiratory droplets that can spread the coronavirus, but stressed it must be tightly fitted to the face.

A family walks wearing masks in Downtown Los Angeles on March 22, 2020, during the coronavirus (COVID-19) outbreak. – The US president on March 22 said he had ordered the deployment of emergency medical stations with capacity of 4,000 hospital beds to coronavirus hotspots around the United States. (Photo by Apu GOMES / AFP) (Photo by APU GOMES/AFP via Getty Images)

Based on the study, the CDC revised its mask guidance, saying that masks should be secure to the face without gaps that allow droplets to escape, and adding that wearing a cloth mask over a disposable surgical-type mask is vastly more effective in preventing the spread of the virus.

The study found that wearing a standard disposal mask blocked 42% of particles from a simulated cough, while a cloth mask blocked 44%.

“The combination of the cloth mask covering the medical procedure mask blocked 92.5% of the cough particles,” according to the study.

A similar improvement was noted by using a single disposable surgical type mask with the ear loops tightly knotted on each side to eliminate gaps on the face.

The CDC’s website was updated Wednesday, urging people to wear tight- fitting masks. It suggests choosing a mask that has a nose wire that the wearer can custom fit around the bridge of the nose to ensure a tighter fit. It also suggests wearing a mask filter or brace over the mask to “prevent air from leaking around the edges of the mask.” Wearers should ensure a tight fit by cupping their hands on the outside edges of the mask to check for gaps.

“If the mask has a good fit, you will feel warm air come through the front of the mask and may be able to see the mask material move in and out with each breath,” according to the CDC.

But the CDC guidance also suggests adding layers of material – using a cloth mask with multiple layers of fabric or wearing “one disposable mask underneath a cloth mask. The second mask should push the edges of the inner mask against your face.”

The guidance warns against wearing two disposable masks, because they are not designed to fit tightly, and also says high-quality N-95 masks should not be combined with other masks.

“The bottom line is this — masks work and they work best when they have a good fit and are worn correctly,” CDC Director Dr. Rochelle Walensky said during a White House briefing.