What would be a good way to pressurize & filter the air in a safe room?

The Oak Ridge National Laboratory's study establishes that an expedient, sealed safe room provides substantial protection from an attack with nerve gas. Positively pressurizing the room increases the protection by insuring against leaks in the room. So the next issues are what can we use to pressurize the room; and what can we use to filter the air introduced into the room.

An electrical air pump appears indicated. AC power would be low maintenance, but by itself does not seem secure enough for me to trust my family's lives on it. A DC source, probably from battery seems essential.

A bathroom exhaust fan in, say, vent piping might provide an AC air pump. Some have recommended battery-powered air pumps such those made by Coleman to inflate air mattresses being attached to gas mask filters to provide pressurized, filtered air for a safe room. However I really wonder about the reliability of those pumps, especially for prolonged use. Gas mask filters are designed for a much lower volume of air than would be produced by a continuous flow from an electric pump. Also I believe that their reliable life is limited to a few hours even when they filter only the breathing of one person. A filter with a longer useful life and capable of filtering a larger volume of air seems necessary.

Hence the quest for a more reliable air pump and a higher capacity, longer-lived filter.

Does anyone have any good ideas?

Thanks,

John