For even more questions to ask a bomb shelter manufacturer, see The 12 Underground Shelter Deceptions That Can Get You Killed

Are You Getting the Best Underground Shelter? 6 Important Questions You Need to Ask Before Buying

1. Was your company’s shelter tested under a real nuclear blast?

What shelter buyers need to know about underground nuclear blast shelter testing:

If any shelter manufacturer claims to have a shelter that was tested by the US Government under a nuclear blast, ASK TO SEE THE TEST REPORT. If the shelters were tested at all, you will probably find that the shelters were tested under a non-nuclear blast, empty, and with no people inside. The US Government is prohibited from testing any shelter with people inside. The only shelters tested many years ago, prior to the development of Finite Element Analysis (FEA) testing, were culvert plate and box shelters under a conventional blast using TNT and diesel fuel.

2. How are your company’s shelters tested?

What bomb shelter buyers need to know underground shelter testing methods:

Finite Element Analysis (FEA) testing is an extremely accurate engineering method used to design aircraft and spacecraft, because aircraft design is so critical, and spacecraft cannot be tested. FEA testing replaced actual underground shelter blast testing in the 1960’s because the computerized FEA tests allows the underground shelter to be tested under many conditions simulating various soils conditions, water tables, corrosion degradation, and pressures, whereas actual blast testing is limited to only one set of ideal conditions. This is why physical blast testing became obsolete.

3. Are round shelters stronger than square shelters?

What bomb shelter buyers need to know about underground shelter shapes:

The military stopped using round shelters more than 50 years ago. Any square or rectangular structure can be designed to meet any external pressure requirement needed. Pressure tanks are usually round because they hold air or fluid that can conform to a round shape. The material to volume ratio can be minimized. That is why underground storage tanks are round. Square or rectangular tanks that are used as pressure vessels are heavier and therefore more expensive BUT they allow people to operate inside the shelter normally at almost 100% efficiency, whereas, a round underground shelter is not more than 70% efficient. Occupants in round bomb shelters literally bump into a round shelter’s inefficiency because the ceiling gets shorter as it rounds into the walls. This is almost always a problem for claustrophobic people. Small, round shelters allow people to stand up only in the middle of the shelter. 30% of the shelter can’t be used because the shape is so inefficient. The smaller diameter shelters like those that are 10 ft. in diameter are even less efficient for people to operate in.

4. Does your bomb shelter have a high pressure (psi) rating?

What bomb shelter buyers need to know about bomb shelter pressure ratings:

A 50 psi bomb shelter pressure rating offers a deadly and false sense of security. The psi rating indicates the distance from Ground Zero. A nuclear blast creating 50 psi pressure may also produce enough radiation to kill shelter occupants within the first 24 hours. Your shelter will survive but you might not. Almost all the underground nuclear shelters on the market today are designed for a bomb blast but not a nuclear bomb blast. Nuclear bomb blasts require protection from the blast pressure and nuclear radiation. The pressure rating refers to blast protection but not to an internal radiation dose at that pressure.

“If the Total Rems in Shelter is lethal, the blast protection is pointless.”

Many shelter manufacturers claim to have absurdly high psi ratings without considering the radiation protection requirements implied by that pressure. A shelter pressure rating must be directly connected to the shelter radiation internal dose. A properly engineered and installed 10 psi pressure rated shelter such as the NORAD S10 Outpost underground bomb shelter, will protect occupants from the direct blast and radiation effects of one 100 KT surface burst at 0.9 miles from ground zero and one 500 KT air burst at 2.1 miles from ground zero. The S10 Outpost shelter will allow a maximum of 8 Rems in Shelter from all sources at  10 psi. A Total Rems in Shelter (TRS) of a maximum of 8 Rems from all sources at 10 psi is referred to as a TRS rating of 8-10.

Always ask about the radiation dose at the shelter’s stated pressure rating. Ask “What blast and radiation will your shelter protect me from?” rather than “Do you have the highest possible psi rating?” Not all bomb blasts are the same. You should understand the shelter’s radiation design dose as well as its pressure rating. If the Total Rems in Shelter is lethal, the blast protection is pointless. In the real world, you want to know how close the shelter can be to ground zero and still offer protection to the people inside. It does you no good to have a shelter that survives a 50 psi blast if you die of radiation sickness inside the shelter.

5. What is the service life of your company’s underground shelter?

What bomb shelter buyers need to know about bomb shelter life spans and bomb shelter warranties:

Poor engineering and corrosion are two of the main risk factors affecting the bomb shelter’s useful lifespan. Shelters that come with a “Workmanship and Material Warranty” do not cover poor engineering and corrosion! The workmanship can be a perfect execution of a terrible design, so your warranty is useless for workmanship problems. Since metal naturally corrodes underground, you cannot point to a defect in materials. The shelter’s lifespan might really be only 5 years, after which it becomes dangerous to enter. A 200 year shelter with a “workmanship and material” warranty is not a 200 year shelter.

“Shelters that come with a ‘Workmanship and Material Warranty’ do not cover poor engineering and corrosion!”

Galvanized culverts used as underground shelters have a very different corrosion environment than when the culverts are used to carry water. Shelters are enclosed in earth, while culverts carrying water are exposed to water and open air. Sacrificial galvanized coatings are constantly degrading. The zinc coating corrosion rate varies widely with pH and wetness. Soils with sulfates, chlorides, nitrates or oxygen in them drastically affect the culvert corrosion rate.

Based on real-world experience, you should expect an underground culvert using sacrificial galvanized coatings to last for between 5 and 20 years. It will corrode at a rate of about 2 to 5 percent per year. The corrosion, at some point in time, will make the shelter unsafe to use.

A manufacturer selling a “200 year” structure with a “workmanship and materials” warranty will refuse to service the corrosion issues because corrosion is a natural process and therefore not a defect in the material.

A structural warranty, on the other hand, covers engineering and corrosion risk factors. The NORAD S-Series bomb shelters come with a structural 30-year warranty. With a structural warranty, the manufacturer is promising to repair at no cost to the customer any structural issues, even those caused by engineering and corrosion factors. Therefore a 30 to 50-year structural warranty really refers to a 30 to 50-year shelter service life time period before the underground anodes need to be replaced. Once the anodes are replaced the shelter will have another 30-50 year service life.

6. Does your underground shelter come with one of the NBC air filtration systems from Andair, Lunor, Bethel, Temet or Safe Cell?  

What bomb shelter buyers need to know about NBC air filtration systems:

A correctly-configured NBC air filtration system is literally the difference between life and death, as the NBC air filtration system is responsible for keeping nuclear, biological and chemical materials away from shelter occupants. Each air filter feature is essential to its life-saving operations.

Perhaps the most misunderstood aspect of NBC air filtration is “residence time,” which is the time the filtered material is in contact with the filtration material. NBC filtration residence time is an all or nothing calculation. Less residence time than the minimum produces no protection — not less protection — from nuclear, biological and chemical threats. US Military NBC Air Filtration TEDA carbon residence time is 0.25 seconds or more to allow for start-ups with a clean filter.

US Military NBC Air Filtration systems have at least 0.25 second TEDA carbon residence time, as well as materials and features ensuring life-saving operation. They are made from stainless steel with continuously welded seams. They have a pressure gage for the pre-filter, a pressure gage for the TEDA carbon filter, and a third pressure gage for the HEPA filter. They have removable filter trays using a Bag-in Bag-out (BIBO) filter change system that protects operators from the dangerous materials caught in the filter. US Military NBC Air Filtration systems use 33 lbs. of 100% TEDA carbon per 100 cfm for long term operations. They have a test port able to access a standard US Army Chemical Test Kit. A viable air filter solution must last at least 30 days to wait out the “fallout period” post nuclear blast.

As of the writing of this article, none of the brands mentioned in the question offer NBC air filtration systems with the required 33 lbs. per cfm, 100% ASZM TEDA Carbon with a 0.25 seconds or great residence time. They do not meet the modern US Military specifications for NBC environments. None have stainless steel housings with continuously welded seams. None have removable filter trays or BIBO filter removal systems to prevent human contact with contaminated filters. None have pressure gages to tell the shelterists when the filters require changing. None of these brands have a good method for testing for chemical agents. None are designed for use longer than 2 weeks in an NBC environment. Some don’t filter chemical agents at all.

All of these manufacturers sell only hand crank models.   Hand crank blowers only work for a few days. When people who are not in good physical shape crank a blower, they exhaust almost as much carbon dioxide as the hand crank blower exhausts. In most cases there is just not enough human horsepower to crank a hand blower for very long and most people become exhausted long before the 30-day danger period is over.  Hand crank blowers do not work for the elderly, young children, injured, or disabled, which are a significant portion of the shelter population. Hand crank blowers will cause the levels of carbon dioxide and oxygen levels to fluctuate inside the shelter resulting in many people getting severe headaches.

NORAD Shelter Systems LLC does not sell NBC air filtration systems by these brands because, at the time of this writing, these companies did not offer adequate protection for a severe NBC environment.