First of all, a disclaimer: I am a mad knitting scientist. That is different than being an actual scientist, particularly the kind of epidemiologist or virologist who might give you conclusive advice on the effectiveness of surgical masks as a protection against the swine flu or other viruses. Insidemex.com will be posting interviews with these people as we and the rest of the world try to make sense of this epidemic and its significance. For the moment, however, this is an investigation undertaken by a curious and crafty lay person looking for practical ways to stay safe and healthy.
The questions at hand: how effective are the surgical masks for sale at the corner pharmacy? And it is possible to make a more effective mask from common household materials?
As I posted on my personal blog a few days ago, my first experience with a global viral epidemic was with SARS in Asia in 2003. The N95 mask-- so named because it in a laboratory setting it filters 95% of airborne contaminants-- was touted as a first line defense against that virus, and significantly better than the simple pharmacy mask. A guest appearance on the Oprah Winfrey show during the 2006 bird flu epidemic solidified its fame.
But what if you can't find the N95 in your area, or if they sell out during an emergency situation? (For the record: I have not tried to buy an N95 myself, but do know of at least one friend here in Mexico City who did so successfully). What if you don't want to fork out as much as $25 USD for a single mask?
The beauty of the internet is that it provides an answer for every question, no matter how obscure. With the hope of finding a simple, inexpensive and (hopefully) better flu barrier than what I could buy, I searched the web for ideas and came across several discussion boards, with recipes for effective mask filters. The gist of the idea is that a simple cotton textile permeated with oil-- a bandanna, say, which has been soaked with petroleum jelly-- could provide an effective virus filter. The science is the same as what's employed in air intake filters on high-performance car engines (and to less desirable effect on your pots and pans or dirty floors): oil can be used to trap dirt and other nasty things.
That's all I needed to know to snap back into 4th grade science fair mode. Here's my experiment, based on what I discovered online. Materials check: one jar of vaseline? Check. Two 100% cotton bandannas? Check. Off to the lab!
Step 1. Heat vaseline in a pan over low heat until liquid. This took just a couple of minutes and the resulting liquid was the consistency of cooking oil.
Step 2. Immerse bandanna in the liquid vaseline, making sure that the entire cloth is uniformly and completely coated. This was slightly messy. You might want to have an old towel on hand to rub away excesses once the bandanna is saturated.
Step 3. Fold bandanna three times from corner to corner to create a triangle of cloththat is eight layers thick. This is your filter.
Step 4. Now, you're going to take the second bandanna and use it as a mask to hold your oiled filter. It might take a bit of experimentation to figure out what's most comfortable for your face, but the basic idea is to fold the top bandanna into a trapezoid that goes just above your nose and just under your chin, and can tie behind your head. Once the shape is right, place the oiled filter in the center of the second bandanna (this should completely cover your nose and mouth...don't leave any gaps) and tie the top bandanna so that you're breathing through the filter.
Making the mask was simple and took less than an hour of time. Its unconventional lookmight raise eyebrows on the street, but the reasoning seems solid and I'm hoping to speak with experts about the science and viability for daily use here. Here are a couple of extra considerations for your own experiments:
Can you breathe? It goes without saying that the more layers in your filter, the greater protection you'll have. It also goes without saying that the same physics apply to oxygen particles as to the flu virus, and it would be a shame to drop dead of asphyxiation while trying not to drop dead from the flu. It was too difficult to breathe through the 8-ply filter, so I cut the bandanna down to a triangle with two layers. I found this to be more comfortable, which makes me more likely to put it on and keep it on.
What about other fabrics? Bandannas are ubiquitous and cheap, but other than being cotton and receptive to the oil, don't seem to possess any special characteristics. One post that I read reported that t-shirt cotton is also fine for the filter.
What about other oils? Petroleum jelly is particularly viscous so I'm sure that it's perfect for this kind of mask. But what about other oils? Olive oil, Baby oil, Crisco? I saw one post that suggested using Vicks VapoRub as the oil. One suggestion: if you do use Vaseline, try and find the regular (unscented) version. All I could find at Woolworth's was the "Baby Fresh" version and prolonged contact with that cloying smell might make you want to take your chances with the flu.
How frequently should you change the mask? According to experts, perhaps the most important thing you do--more important than the materials of the mask itself--is changing your mask frequently. Moisture from your breath can encourage trapped virus particles to multiply on your mask. In fact, replacing a used cheap mask with a fresh one every couple of hours might be more effective than using the same old N95. The bandanna filter is washable, though I couldn't find conclusive evidence as to whether or not it needed to be re-oiled after each washing.
Medical and science professionals in the audience: What do you think of our mask? How robust is our science? And what's the best way for the average person to protectthemselves from airborne transmission of the flu virus? We want to hear fromyou! Post your comments below.