12 Jul Rates of Transmission – What is Close Contact and What About Masks?
We’re hearing a lot about N95 masks, or KN95 masks, but do you know that they actually do? The 95 comes from the fact that they restrict 95 percent of air particles. This is why a person’s health must be considered before they wear an N95, because those with breathing issues may suffer a severe loss of oxygen wearing this kind of mask.
Right now, due to a severe shortage of US made masks, KN95’s are approved for use inside the US, although the federal government routinely puts out a list of KN95’s that do not meet appropriate local standards.
But don’t pick the one with a valve!
The reason people wear masks is to both prevent them from exposing others to droplets from their mouth or nose, and to a much lesser extent, prevent inhaling droplets from others around. However, the construction use N95’s with the valves are designed for construction debris, meaning they block particles during inhalation, but don’t block exhalation, so they don’t protect others.
We also hear about close contact a lot. The CDC has re-defined it a few times, but right now it’s generally 15 minutes of time within six feet of another person without a mask.
Do the masks work?
There is some controversy surrounding this, with one analogy that it’s like putting up a chain link fence to stop a mosquito. But there is evidence that the wearing of even surgical or cloth masks slows the spread of COVID-19. There is no 100% guarantee, but most doctors agree there is some reduction of risk.
And there have been some near misses where masks seemed to have made the difference. Take this incident in late May in Missouri, highlighted in this Washington Post article. Two hair stylists at one salon were working while having symptoms of COVID-19. One saw 56 clients, the other saw 84, working closely with each for an average of 30 minutes. Both hairstylists were confirmed COVID-19 positive. Local officials braced for a terrible outbreak, but both the stylists and the customers were required to wear face masks, cloth or surgical. Of the 140 people exposed, 46 decided to get tested, and none were positive, with the others never having symptoms or wanting tests. https://www.washingtonpost.com/business/2020/06/17/masks-salons-missouri/
Surgical masks tend to allow for easiest air flow, and may be more comfortable for elderly people or those who are compromised. They may also provide better protection from particles than cloth. The most effective masks are the ones typically reserved for health care workers doing invasive procedures or working with COVID-19 patients, the N95. One study showed that cloth masks had about 60% less ability to reduce particles than a typical 3M N95 mask.
The general rule is that whatever mask is worn; it should be clean and cover the nose and mouth. Johns Hopkins even puts out this best practice for removing a mask:
- Wash your hands or use alcohol-based hand sanitizer containing at least 60% alcohol.
- Don’t touch the front of the mask or your face.
- Carefully remove your mask by grasping the ear loops or untying the ties. For masks with a pair of ties, unfasten the bottom ones first, then the top ones.
- If your mask has filters, remove them and throw them away. Fold the mask and put it directly into the laundry or into a disposable or washable bag for laundering.
Clean your hands again.