Air Filter System
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Outside the EOC Front Entry
Air Filter System
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Shelter Air Filtering System
I find the air filtering system in the Old Dallas EOC absolutely fascinating. On this page I try to show the layout of the air filter system. It was very difficult to get good overall photos in the cramped confines of this area so I have included floor plans and air flow plans of the filter system to, hopefully, make the description easier to understand. I have decided to call the two sections that make up the system the "air filter system" and the" gas filter system". Maybe I wasted my time with all this and no one else is that interested but what the heck here it is anyway. Click all images and plans to see larger.
The Old Dallas EOC shelter has an elaborate air filtering system that consists of two sections. There is a large bank of air filters for filtering out fallout particles and there is also a pair of Gas Particulate filters as well. Each system of filters uses a separate blower to pull air through their respective filters. From what I was able to figure out by looking at the system it appears that each set of filters is used by operating the blower for that set of filters. The blowers for each system feed into the air conditioner for the shelter. The air is then fed through the air system into the shelter and then out the exhaust system at the back of the shelter. The air exhaust system blower is located in the Men's Restroom. I saw no evidence of any type of filtering in the exhaust system. The air is then fed out through the exhaust anti-blast valve on the surface.
New information October 2011.
I found out in October of 2011, thanks to Matt Garret of Richardson Emergnency Management, that the bricked-in area in the corner of the air system intake chamber is a time capsule put in place by the City of Dallas. The time capsule is marked with a plaque located on the cinderblock wall facing the escape hatch. I couldn't see it when I was there because of all the old files and junk piled against the wall. Oh. Mr. Garrett used to work with Dallas E.M. Thanks Matt for the information!
Air Intake Anti-Blast Valve and Air System Intake Chamber
The above left photo shows the air intake anti-blast valve on the surface. The anti-blast valve was to close and seal the shelter from the increase in pressure from a nuclear blast wave. The valve would then open again when the outside pressure returned to normal. I believe the valve is spring operated in some way. There were no visible exterior connections to the vlaves. There is also an anti-blast valve on the air exhaust out of the shelter as well. The emergency escape hatch can be seen about two feet to the right of the air intake.
Interesting Information About The Anti-Blast Valves
I wondered about the city "going the extra mile" to have such serious hardware installed on this shelter. It turns out that the anti-blast valves in this shelter have a very interesting history which I discovered during a visit to the City Of Dallas Municipal Archives in March of 2010. The anti-blast valves were supplied to the city as surplus property to the city from the Nevada Test Site. They were made available to the city for only the cost of shipping them to Dallas. I located a letter in the construction records for this shelter which stated that the valves were available to the city as surplus because they had completed their testing at the Nevada Test Site. It says everything in the letter except that these valves underwent actual nuclear blast tests but they very well may have. I don't see why they would have been "tested" at the Nevada Test Site unless that was the case. Find the documents from the Dallas Municipal Archives here.
The above right photo was taken from below, inside the air intake chamber, inside the shelter. This is looking up into the air intake chamber from the door (the door near the light blue Air Filter Bank in plan of air sytem at top of this page) of the air filter chamber. The ladder on the wall leads up to the escape hatch. The other round hole to the left in the ceiling is the air duct that leads up to the air intake anti-blast valve. Air coming into the shelter enters this chamber first before passing through the air filter bank filters (light blue Air Filter Bank in plan at top of page). The air filter bank is immediately to the left ands behind from where the above right photo was taken.
Air Intake Chamber And Air Filter System
The above right photo was taken looking through the door next to the air filter bank seen in the plan (light blue) at the top of this page. The filters are next to the door leading into the air intake chamber. The air intake chamber is full of old files boxes piled about 3 feet deep as you can see through the door opening. The air intake anti-blast valve and ladder to the escape hatch are located looking up through this door opening.
Air Filter System Blower Inlet Duct
The above right photo shows the same duct seen in the above left photo from the other side of the wall in the mechanical room. The top of the door to the air filter room can be seen at the right lower corner of the photo. The small shelf on the wall next to the door is the mount for the air filter system intake blower. With this blower operating air is only drawn through the air filter bank filters and delivered to the air conditioning system. The round silver air ducts were the ducts that supplied air to the generators in the mechanical room. Notice these ducts aren't on the outlet side of the blower but in the inlet side. The gray air filter stage blower can be seen between the two silver generator ducts. The outlet for that blower is the main duct coming out just past the duct that the silver generator ducts attach to.
Schematic View Of Air Filter System In Operation
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Gas Air Filter System
The above right photo is what you see when you look through the small hatch that leads into the gas air filter room. The lower gas air filter is shown in this photo. The galvanized metal wall that divides the air intake chamber in half is visible behind and above the gas air filter. This room is about 5 feet by 5 feet square. Click the photo to see a larger version. The first line on the filter label reads "FILTER, GAS-PARTICULATE, 600 CFM, M-1" The upper filter is the same type as this lower filter. Both filters are sealed to flanges in the metal wall that divides the air filter room with this gas filter room. To use the gas filters in the air system the air would have been first drawn through the air filter bank (light blue in plan at top of this page), through these gas filters (green in plan at top of this page) and then through the gas filter air blower and into the shelter.
The above right photo shows the gas filter system air blower. The duct behind the blower is the same duct seen in the above left photo. This unit is quite a bit larger than the air filter system blower. Maybe it is larger due to the greater resistance of air flow through the gas air filters. The main blower bracket can be seen in the upper right corner of the photo. Both of these blowers duct into the air conditioner.
I didn't think to look how they switched between the two different filtering stages. I don't know if there was a damper in the ducting to switch between ducts or if the blowers were just run alternately respective of which filtering system was to be used. I can't see any kind of duct switching mechanism in the photos but it seems like there would have to be something to close off the duct of the system that wasn't being used. If I get a chance to go back that will be one of the first things I look at.
Schematic View Of Gas Filter System In Operation
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