The CDC has confirmed that face masks with valves and vents on them—which have become increasingly more popular lately because of their high-tech look and breathability—aren't, in fact, good for you, nor do they help prevent the spread of COVID-19.

As the war to make sure people wear masks rages on, the CDC included in its guidance update last week that masks with valves that are commonly worn at dusty construction sites are not meant to be worn casually to replace other, vent-less masks.

"The purpose of masks is to keep respiratory droplets from reaching others to aid with source control,” the update read. “However, masks with one-way valves or vents allow air to be exhaled through a hole in the material, which can result in expelled respiratory droplets that can reach others. This type of mask does not prevent the person wearing the mask from transmitting COVID-19 to others."

The Washington Post also highlighted that 3M, the company that often produces these valved masks, has it clearly stated on its website that air is inhaled through the fabric and humid air is then exhaled through the valve, which makes the mask great for working in spaces with dust, in the air but not a virus.

Warnings against masks with valves or vents have been issued throughout the summer.

Also included in the CDC's latest update was the info that plastic face shields are not encouraged to be worn by babies or infants, masks should not be worn by babies under the age of 2, and masks should still be worn in public settings where social distancing guidelines aren't able to be maintained. You can read all of the CDC's new updates here.