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Fallout Shelter Ventillation Help Needed

Fallout Shelter Ventillation Help Needed

Fallout Shelter Ventillation Help Needed


I am building a fallout shelter for my family and need help with the design of the ventillation so we don't suffocate if we ever have to use it. Secondary use of the space is as a root cellar.

I have a question near the bottom of this post, but here is the background information you will need to answer the question:

Shelter dimensions are 10'w x 10'd x 8'h
All walls are concrete filled block, below grade and backfilled. Roof is 11" concrete slab supported by steel beams, sealed air-tight.

Only opening is tight fitting 36" door into stairwell area.
Top of stairwell has bilco basement steel doors, these doors would be sealed with plastic & duct tape during fallout use, minimal air leakage.

Incoming air supply via 4" pvc pipe low in wall, filtered outside of shelter to remove radioactive particles using HEPA filters. Blower or fan on inside of shelter to provide positive pressure to ensure all air flows outward (no incoming unfiltered air).

Exhaust air via 4" pvc pipe with HEPA filter outside of shelter, located on top of opposite wall.

Backflow valves located on inlet/outlet lines, battery powered CO2 alarms mounted in shelter.

Filtered air comes in, blower or fan creates positive air pressure and freely circulates filtered air inside of shelter, then stale air exhausts due to positive pressure via outlet. Pressure differential should overcome HEPA filter and backflow valve on outlet.

I want to be able to swap out blowers/fans easily from 115v AC to 12v DC if needed, will have large deep cell 12v dc batteries for backup power requirements. Therefore, blower/fan will be installed inside shelter and will be pulling air in via inlet and then distributing the filtered air via ceiling vents.

Normal occupancy of shelter during fallout conditions would be 2 adults 2 children. Thanks in advance for reading this post and considering helping me with ventillation design.

Question follows:

I need help chosing the correct blowers/fans for this application. Two of the blowers I am considering are:

Grainger DC Blower,12 VDC,79 CFM
Item # 3FRG6
DC Blower, Forward Curve, Direct Drive, Wheel Dia 3 15/16 In, CFM @ 0.000-In. SP 79, Voltage 12VDC, Single Phase, Full Load Amps 2.8, RPM 3440

Grainger PSC Blower,115 Volt
Item # 1TDP3
PSC Blower, Forward Curve, Direct Drive, Wheel Dia 3 15/16 In, CFM @ 0.000-In SP 75, Voltage 115, 60 Hz, Single Phase, Full Load Amps 0.45, RPM 3016

Are these blowers appropriate, or do I need another size or another type of product? I am open to any suggestions. I do know that there are specilty filters & blowers designed for these applications, but they cost thousands of dollars and I cannot afford them. Any help will be greatly appreciated.

Thanks again,


RE: Fallout Shelter Ventillation Help Needed

The CFM that is required in the shelter s/b based on the number of people, fuel fired appliances, bath room.  Forget the battery backup, instead I would rather bank on a small diesel operated generator.

The data that you provided only provides free air delivery.  Grainger has fans with characteristic data.  You must also calculate under various air flows the total friction loss thru the inlet and outlet pipes, elbows, louvers, screens, etc...; both data can the be plotted and where the curves intersect will be approximately the CFM that the shelter is getting.

RE: Fallout Shelter Ventillation Help Needed

I'd watch the static pressure, as pushing through two HEPA filters can have a pressure loss as high as 2" w.c.

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