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28 July 2006 at 11:02 am #3364
This was sent to me by a microbiologist in Washington and he has informed me that N95 masks being used by poultry farmers although very cost effective is completely useless against H5N1 virus. He refers it to trying to filter sand with a pasta strainer! The H5N1 virus is so much smaller than .3um. Why on earth would anyone want to wear a N95 mask which is only 95% effective? Would it not be more prudent to wear a mask that is 99.99% effective? Would it not be wiser to actually use a mask that’s been tested with biological agents instead of salt particles? It’s kind of like building a boat and spraying it with a hose then telling everyone it will float. I understand that N95’s are inexpensive and yes better than nothing. But why is everyone so quick to accept it as being the best or only solution. Their are masks out there that will give you 99.99% protection. I’ve read that the H5N1 virus is attached to droplets and that the N95 will stop it from passing through. What about the 5% that might get through. How long will the 95% efficiency of the mask last? Not all face masks provide the same level of performance hour after hour of use. Studies show that when subjected to bio-aerosols, the performances of most face masks deteriorate significantly over time unless there is a antimicrobial agent which protects it against microbial deterioration of the filtration media. What is N-95? Filters and infectious particles Particles greater than 5 microns fall out of the air Particles 1 – 5 microns in diameter can enter upper airways 0.1 – 1 micron particles enter lower lungs and alveolar ducts Examples of particle size: Viruses 0.02 to 0.3 microns – N95 mask not effective Bacteria 0.5 to 10 microns – N95 mask effective Mold spores 1 to 70 microns – N95 mask effective Fungi 2 to >200 microns – N95 mask effective Particulate filter efficiency is based on ability to remove particles greater > than 0.3 microns in diameter (medial aerodynamic diameter of 0.3 um) It is also very important to note, that although the CDC recommends these products as suitable levels of protection against the H5N1 virus, the testing criteria used to certify these products does not include any biological agents. NIOSH only tests the filtration efficiencies of N95 facemasks against salt particles, and does not currently employ any standards to test against live agents. http://www.cdc.gov/niosh/pt84abs2.html 42CFR part 84 Under the new particulate filter tests, NIOSH will certify three classes of filters, N-, R-, and P-series, with three levels of filter efficiency, 95%, 99%, and 99.97%, in each class. All filter tests will employ the most penetrating aerosol size, 0.3 µm aerodynamic mass median diameter. The N-series will be tested against a mildly degrading aerosol of sodium chloride (NaCl). The R- and P-series filters will be tested against a highly degrading aerosol of dioctylphthalate (DOP): http://www.health.state.mn.us/divs/idepc/dtopics/infectioncontrol/ppe/comp/n95.html http://www.cdc.gov/niosh/npptl/usernotices/pdfs/Nanoguard062906.pdf Nanoguard Mask Warning28 July 2006 at 11:52 am #4327Martin WParticipant
N95 masks used during SARS (a virus) and effective, unless – say – someone push up the mask to scratch itchy nose.
I tried one, once, during the outbreak: horribly unconfortable; hot n humid air, even worse than normal hot n humid air in HK. Tried the nigh-on useless (unless you happen to have a disease yourself and don’t want to pass it on) paper masks. Otherwise, with SARS mainly in hospitals, went mask free.
Can’t imagine more than tiny number of people in areas actually affected by H5N1 virus (rather than by bird flu fearmongering) will use masks; and those that do perhaps in factory farms, where masks etc should be supplied by companies, or veterinary support etc, also supplied with masks.
Otherwise, these masks surely beyond reach of people in areas really affected by bird flu; and unlikely to be worn anyway.
While if aiming for sales to the paranoid: well, shame on viraldefender.com.
See also this summarised paper on CDC site, about making masks from t-shirts; not ideal, but judged effective:
http://www.cdc.gov/ncidod/EID/vol12no06/05-1468.htm7 May 2009 at 5:01 pm #4611Anonymous
I raised this issue at work and this is what I was told: in order for viral particles to become airborne and capable of traveling through the air, they need to attach themselves to something (i.e, dust particles, respiratory droplets, mold spores, et etc), that has enough mass to be lifted by air currents, and viral particles are too small to travel through the air by themselves.
I’m still pondering the explanation that I was given.
I previously thought, perhaps erroneously, that getting sick had to do with the amount of viral particles to which one was exposed, and it wasn’t exposure per se that made one sick, but rather the amount of viral particles that one was exposed to, and respiratory droplets measuring 0.3 microns or larger contained enough viral particles to make one sick.
I am not a virologist or researcher, I’m just your average layperson, and I do not know the correct answer to these questions.
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