Wednesday, October 15, 2008

More discussion about masks - part 2

I would like to thank Sealed Air -Cryovac for inviting me to speak with its employees about allergic diseases today. One of the best parts of any interaction is the questions I get. Here are some of the questions and answers.

1. What does the number 95 in N95 stand for? I have written previously about masks. In 1995, the federal government issued new standards for the certification of respiratory protective devices (a.k.a. masks and respirators). The percentage penetration of particles with a maximum size of 0.3 µm median diameter was measured using the protective devices. 95 means that 95% of particles were blocked by the protective device. Similarly 99 means 99% of particles were blocked by the protective device. 100 means that 99.97% of particles were blocked by the protective device.

How good is the 0.3 µm standard? Very good. For comparison, human hair is 80-100 microns, dust mite droppings average 10-24 microns, pollen grains average 24-50 microns, mold spores range from 3-100 microns, cat dander's mean is 2.5 microns (range 1-10 microns).

3. What is the best type of mask to get? There are several important factors: cost, durability, activity, need for high degree of filtration 100 vs. 99 vs. 95, and often overlooked fit. Without a tight seal, air will leak around the protective device and completely ruin the intent - protection from airborne particles. This is often overlooked, even in the medical setting. Some favor the premolded white or blue masks, while others like the masks that open up like a folding fan over the mouth and nose.
It does not matter which you choose, so long as there is NO air leakage. Make sure of this! Thanks to Mr. Mungo for reminding me of this critically important point.

4. What do I think about ozone generators? They are potentially life-threatening devices. Ozone is a highly toxic gas. At no time would I ever volunteer to be around ozone. On earth, it can found fortunately in a few places: due to lightning, on hot and smoggy days, around an actylene torch, and in the earth's outer atmosphere. Recall, when the Environmental Proectection Agency (E.P.A.) measures high counts of ozone, the EPA issues a warning for people to stay indoors with the a/c running, so as not to breathe the ozone. Recall the ozone layer protects the earth from the sun's ultraviolet rays, which would otherwise kill us all.

5. An aside, I'll be writing more about air filters in the future.

If you have questions, ask your doctor!

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