Chuwa,
This looks to be a particle mask only; it won't filter any gases. While it is great to be using a mask, the size of particles is important. This is because the very small particles are what is called "respirable," rather than "inhalable." Larger particles are trapped in the upper regions of the respiratory system. They don't get into the lungs. But the very small ones get all the way into the air sacs of the lungs.
The half-face mask that I have worn has a P-100 filter on it. That filter will filter particles down to 100 microns, which is quite small. Actually, it will also filter the much smaller nanoparticles too. I say this because diesel exhaust, and the wood smoke that some showed photos of above, contain very small particles which qualify as nanoparticles. To gain an understanding of nanoparticles, you can go to the NIOSH website:
http://www.cdc.gov/niosh/topics/nanotech/
There is also a very interesting discussion of nanoparticles at this site:
http://www.kqed.org/quest/television...n-a-nano-world
Most HEPA filters will also filter out nanoparticles. I think that this cycling mask would also, but I cannot say as that mask has not been tested.
There is one other aspect, and that has to do with fit. I was just fit-tested with the half-face mask I have been using, using a much better protocol for quantitative fit testing. My mask failed this test, perhaps because as I have aged, my face has changed a bit. Here is an explanation of these procedures:
http://www.osha.gov/SLTC/etools/resp...ttesting1.html
Fit testing can be done using either quantative or qualitative tests, and these bicycle masks really need that kind of test to ensure a fit. Without that fit, you will be breathing some air around the seal instead of through the filter. While most will go through the filter, contaminants can still get through. You can get these fit tests done at a safety supply store, as most of them will do the tests on the wearer.
The NIOSH approved half-face masks, with a Technical Certification number (TC number) have the advantage of allowing the use of cartridges which filter out gases, such as acid gases or organic vapors. When combined with the HEPA filters (High Efficiency Particulate Filter), more toxic airborne materials can be filtered than what the bicycle filter will get.
John