Okay, have an idea about this story called Gas Mask, and I know this may be more suited for a research thread, if there is one, but please I need help in two areas. A. Okay, how long can someone wear a gas mask before they have to take it off? This is important because I'm thinking of a story where someone may have to spend multiple days outside in an enviroment polluted with deadly chemical weapons. B. Are there any normal building that are sealed against chemical weapons? If not, how would one perhaps go about sealing a building against chemical weapons? I mean, the character has to be able to take it off sometimes.
A. It depends on the type of filters used in the gas mask. Most can last days or even weeks. As you breathe in air, your lungs suck the air through filters of activated charcoal and other media that filters out all the nasty and dangerous stuff in the air. It is much more difficult to breathe through a gas mask filter, than it is to breathe normally. Police SWAT and military training makes you do daily routine tasks, while wearing your mask and other protective gear, so that your lung power gradually builds up strength and gets used to it. B. Any building with an airlock entrance, sealed fallout shelter/bunker doors (with rubber gaskets) and any vehicle with an air tight hatch (submarines and newer models of tanks/armored personnel carriers) can be sealed against chemical reagents. In an emergency, you can "Seal" a normal solid door (no windows/vents) with either rubber gaskets, foam or plastic used for sealing, and a layer or two of duct tape around all exposed cracks on the outside edge of a door. Chemical weapons such as Cholorine Gas or Mustard Gas tends to condense and settle over time (Which is why in World War I, where such agents were first used, soldiers had to don their gas masks and evacuate the trenches before the gas settled in the low areas). Therefore in theory, the upper stories of buildings would offer protection against gas weapons after the initial gas attack started to condense and settle.
Sadly, after talking with a friend, it appears I'll need a new chemical weapon to exist for this. There's a reason people keep on using Anthrax in stories, it actually works that well. VX is more of a liquid substance that you would need full on protection for, and the enemy would need to drop tons of it. But I think I can make this work, I'll need a new weapon though. Not one that exists. Fortunately, this is easy. All you have to do is turn smog into something deadly. There's so much of it in the atmosphere that it would kill everyone. Add some chemicals to smog, somehow, and you have an apocalypse on your hands. So, along that line of thinking, if smog did become deadly, where should someone go? Also, where would someone get a gas mask?
An army surplus store would probably sell a few. Fire stations/police/Hospitals would probably have a few of the oxygen masks that you can wear while moving through a building. Just adding to this. Duct tape can be used to seal a room in case of bio chemical weapons/airborn poisons, but that area would not remain safe for very long. The adhesive of the duct tape will make the room airtight, but without a renewable source of oxygen, you would suffocate.
Army Navy surplus stores, Police Supply Houses, Mail Order, Ebay, Gun Shows, Military collector's shows, Emergency Preparedness/civil defense suppliers. Here are a few commercial websites. http://www.cheaperthandirt.com/SearchResults.aspx?catid=296&site=All+Products&num=15&q=gas+mask http://www.andrewsmilitarysupply.com/Gas-Masks.html http://www.bestsafetyapparel.com/gas-masks.html http://www.approvedgasmasks.com/mask-gas.htm
This depends a lot on training and conditioning, as Lothgar has said. Somebody who has trained using a gas mask will be better off than somebody who is wearing one for the first time. People unused to a gas mask can develop claustrophobia and or hyperventilation. In the worst case, they are inhaling and exhaling so fast that they are only recycling the air inside the gas mask (instead of pushing the air out through the filter and inhaling fresh air through the filter), and can suffocate unless they pull the mask off and receive basic treatment. Wearing a gas mask for multiple days is extreme, though, unless this is an extraordinarily comfortable gas mask. Eventually, the filter will be saturated and need to be replaced. How quickly this happens depends on the kind of filter, and a few days is stretching it for most modern filters. Modern masks have a special port for drinking (you need a straw), but there is no way to eat anything solid without removing the mask. If by "normal" you mean regular houses/offices/factories then no. However, there are some buildings and rooms that are sealed, such as refrigerated storage rooms, chemical tanks etc. Note that many buildings built in Cold War Europe (and, in Switzerland, until today) are equipped with air raid and fallout shelters in their basement. These are clearly NBC-protected, and the "parent" buildings above could be almost anything from primary school to old people's home. In principle, you can seal almost any building against many chemical weapons reasonably well. It depends on the agent being used and how it is being dispersed. You don't even have to seal all doors/windows etc. absolutely airtight. Placing wet towels around the edges of doors and windows is a start. Not opening them once the agent is in place is a must, of course. The roof can be very hard or very easy to seal, depending on how it is contructed. Chimneys would have to be blocked as well. Many chemical weapons are delivered as liquid agents, sprayed from aircraft or delivered by airburst artillery rounds. You don't strictly need a gas mask for traversing an area contaminated by these once they have settled to the ground and it has rained once or twice, but tests have shown that residual contamination will remain for weeks on the underside of objects and in small nooks and crannies, and you will most likely prefer to wear a mask just to be on the safe side. Chemical weapons are seen in warfare today more like area denial weapons, such as mines, which delay and discomfort the enemy but do not cause widespread death or damage (since nearly all armies have strong NBC defence these days). A chemical weapon delivered only as a gas is not very effective because it disperses rapidly with the wind. This removes the contamination aspect and consequently does practically no harm to protected troops or installations hit. It is only effective in the first instants of use, or if the target has absolutely no protection. Note that gas masks sold at army surplus stores, gun shows or ebay usually are not sold with a brand new filter. Usually, the filter is either a mock-up used for training or a long-saturated filter that no longer has any protective properties. The fire services generally do not use gas masks, but, as noted above, oxygen supplies like scuba divers. This is because it is assumed that inside a burning building, oxygen will be very scarce due to its consumption by the fire. Such a tank is obviously as effective or even more so than any gas mask, but the endurance is limited by the volume of the tank (and consequently, by its weight etc.). A good solution for people who only have to go into a danger zone for a few minutes and who can fall back on supply trucks nearby, not a good solution for somebody who is going to trek through a contaminated wasteland for days on end.
