The Reality Of Underground Shelter Types And Ratings

by Walton McCarthy

What is a “BUNKER”?

“Underground bunkers” were shelters designed to protect occupants from the bomb blasts of World War I and WW II. A bunker is an empty structure incapable of protecting occupants from modern warfare threats. A bunker typically does not have a life support system or any air filtration. It has a 0 psi overpressure rating, meaning that it is only effective for protection from small air dropped bombs like what was used in WW II in England . A bunker is a very short term structure considered obsolete by modern standards since it does not meet any established engineering standards for radiation shielding, chemical weapons air filtration, biological weapon air filtration, and it is not suitable even for the duration of a typical hurricane.


A survival shelter is a cheap short-term shelter that has little or no published performance data, has no published Radiation Design Dose from overhead or from the entranceway that the shelter is designed for,  has no published ratings for pressure,  no published internal radiation doses that shelterists can be expected to receive,  does not list the distance from ground zero that the shelter is designed for and  usually has a weak or no warranty.  This type of shelter has a short-term air filtration system and meets virtually no commercial or military standards, and meets no manufacturing standards.


A fallout shelter is designed primarily to protect shelterists from gamma radiation during the fallout period. This type of shelter has a rating of 0 psi of overpressure. Like all underground shelters, it should be water controlled and must provide for a twenty-eight-day period of fresh air, light, heat, flushable toilet, water, food, sleeping, radio communications, and usable space. In general, it must meet all the requirements of the blast shelter except for those relating to overpressure and temperatures from sustained fires. The shelter is a dual-purpose shelter if it can also serve as a basement or extra housing facility. Personal or family shelters are designed for use by up to ten people. A group shelter is made up of a number of family shelters, where there are two or more families together. These shelters may be connected through a common tunnel or just grouped together to make a community shelter.


This is a shelter meeting all the requirements of the fallout shelter plus a resistance to overpressures from 1 to 9 psi. It is not capable of shielding from initial nuclear radiation (neutron radiation).

S16x40 Bomb ShelterWhat is a “BLAST SHELTER”?

A shelter meeting the requirements of a fallout shelter and designed to protect its shelterists from the effects of blast, sustained fires, and overpressure from 10 to 40 psi is a blast shelter. Above a 40-psi overpressure, the shelterists will need to be restrained in seat belts. The blast shelter must also be specifically designed to protect the shelterists from large doses of neutron radiation. Above 50 psi the shelterists would be severely injured, even if the shelter is designed to withstand the blast and radiation. Just as a chain is only as strong as it weakest link, the shelter’s weakest link can be blast pressure resistance or radiation shielding. A properly-rated 40-psi shelter must be able survive the blast undamaged and must be able to provide radiation shielding at the 40-psi level. It makes little sense to survive the blast and then die of radiation sickness a few days later. A shelter psi rating is based on three factors, 1) the shelter pressure rating, 2) the shelter radiation shielding dose, and 3) the hatch and air manifold design. It is erroneous to claim a 30 psi rating for a shelter, if at that distance from ground zero, a lethal or sickening dose of radiation enters the shelter from overhead or the entranceway. Below at 0.5 miles from ground zero an overpressure can be expected in the 30 psi range. A shelter at this distance with 48 inches of earth over the crown of the shelter ceiling (44 inches in the table) would allow approximately 291 rems inside the shelter which would be lethal to the shelterists. Any shelter with 48 inches of earth over the shelter ceiling should be rated a 0 psi making it a fallout shelter. The doses in this table are from overhead only. There are other tables showing the entranceway doses. The radiation doses from all sources, overhead, entranceway, emergency escape, air ducts, all allow radiation to enter the shelter. Radiation from all sources must not exceed 25 rems in the first 30 days. The goal would be to design the shelter for a maximum of 5 rems from all sources of radiation. This rating system is known as the TRS rating or Total Rems in Shelter. A shelter with 48 inches of earth (nearest lower number is 44) would have a TRS Rating of 23-10 meaning that the shelter would allow 23 rems of radiation to enter the shelter at the 10 psi distance.