The Puget Sound Coast Artillery Museum at Fort Worden.
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This section is still being written, so there will be additions and changes when I have time to work on it.
Air Filtration Systems (More details and photos coming soon)

At the beginning of WWII there was considerable concern about the number of casualties caused by gas attacks in WWI. Because of that, during WWII critical facilities were provided with gas filtering capabilities so that they could function and survive in case of a gas attack. They apparently weren't called 'filters' though, based on the labels and the building diagrams we have they were referred to as 'gas collectors' and mounted in 'collector rooms'. Two structures on Artillery Hill were modified to provide protection from poison gas attacks, and two new structures had gas protection designed in. At the time these were designed and built it's likely that no one involved knew about the radiation dangers from the then 'Top Secret' atomic bomb program, but it turned out that the filtering used for gas would also work for radioactive fallout. Because these types of structures were also designed to be protected from shell fire, the radiation protection was even better; the collectors would remove any radioactive fallout/dust, they all had thick (1.5 to 5 feet) concrete walls and ceilings and they all had earth at least over them, and in all but one case around the walls as well. This was probably enough to block any radiation from coming in through the walls or ceilings. One built into a hill side has a 5 foot thick concrete ceiling covered with 25 feet of dirt, and dirt on all sides, with only a tunnel access.

Layout diagram

The basic principles of the gas protection systems in all 4 were very similar, but the details varied. Click the image at right for a representative diagram showing the basic design with some notes. It's also available as a PDF file. One critical requirement is that the building maintain 'positive pressure' where the air pressure inside is higher than it is outside, that way any leaks would let clean air out rather than potentially contaminated air in. While the pressure difference didn't need to be very much, it did require that there be an airlock that would allow personnel going in and out to equalize the pressure without depressurizing the entire facility. All of the structures had pressure relief vents with a one way flapper valve on them, usually in the airlock. These valves worked the same way as dryer vent pipes today, where the air pressure would simply lift the valve plate and let air blow by, the difference is that these flappers are steel instead of the plastic or light sheet metal on dryer vents, meaning it needed more pressure to open them. The weight of the flapper valve determined the pressure difference. All of the systems had a way to bypass the air filter allowing fresh air to be blown in the facility without using the filter when it wasn't needed.

The airlock was also the logical place to put the decontamination system since anyone coming in would need to be cleaned off before entering the main portion of the facility. The decontamination system consisted of a vertical 6 inch cast iron pipe with some fittings. Small holes were drilled in the pipe and the fittings which would allow pressurized air to blow on someone standing in front of it. An air intake pipe would suck up the contaminated air and return it to the collectors to be filtered again. Since poison gas/powder is heavier than air the intakes were usually very near the floor. Theoretically this would blow the contaminates off of the person and their clothing/equipment, then suck the contaminates back to the filter instead of letting them swirl around in the airlock. This probably worked OK in dry weather, but if the person coming in had been out in the rain (which happens a lot around here) the contaminates may have stuck to their clothing and other steps would probably be necessary. All the airlocks had a switch that turned on a blower if needed and operated two valves on the air lines. One valve would shut off the normal intake lines bringing in fresh air from the outside and cause the pumps to suck in air from the intake in the airlock, the other would shut off filtered air to the facility and cause it all to blow into the airlock, through the decon system. Since all the air that would normally go into the full structure was blowing through the small airlock, it was probably fairly well pressurized with a high rate of flow.

All four facilities had piping to bring outside air to the filters and then into the facility. Two (the HECP and the temporary HDCP) had hot water boilers connected to heat exchangers incorporated in the air circulation system, the GPMTCP had steam radiators with the boiler outside the protected area and pipes that circulated the hot water without bringing in contaminates, By using closed loop hot water systems the heater could be outside the gas protected area since it didn't matter if the combustion air was contaminated. If the heaters had been inside the protected area a lot more filtered air would have been required for the burners. Tolles had fireplaces which would have had to be closed off in case of a gas attack. None of the four had any actual windows although the GPMTCP had an upper observation booth with slit windows, the HDCP had two ceiling vents and two vents into outside underground rooms and Tolles had some holes drilled through the thick concrete walls to allow air flow for the fireplaces. All the openings were fitted with "gas tight" closures that would seal them off in case of a gas attack. In structures with ceiling vents, they also had valves that could be closed.

Click the bold name of each structure to see some photos related to the air filtration system.

The two modified structures were:

The two new structures were:

CAM Logo CAM Logo
Puget Sound Coast Artillery Museum
Building 201
Fort Worden
200 Battery Way
Port Townsend, WA 98368
(360) 385-0373

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Page Revised May 28, 2015

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