Frequently Asked Questions
about the Safe Cell
Click on the question to see the answer:
Both the 60 and 120 CFM Safe Cells are designed to work with four inch diameter ventilation pipes for both the intake and outflow. If you are using blast valves in a concrete shelter, you should run four inch penetration pipes through the wall or ceiling and terminate them flush with the inside wall or ceiling. The blast valves will mount right over these penetrations on the inside of the shelter with the included concrete wedge anchors and gaskets. Be sure you account for the 12.5 inch blast valve mounting flange.
The intake and outflow ventilation pipes need to land inside the shelter on opposite corners or opposite walls. That way, the filtered air has to transit the entire shelter before it’s kicked it back outside. This will ensure that the oxygen is replenished and the carbon dioxide is removed throughout the shelter.
You can integrate an airlock just inside the door using two overpressure valves. They are one way check valves. One on each end of the airlock will ensure that all air is flowing outward. The airlock should be as small as practical so it completely flushes with filtered air as fast as possible. Many people locate the bathroom right by the door and use it as an airlock so that odors and moisture are directly removed from the protected space. This also allows you to use the shower to decontaminate when re-entering your shelter.
60 decibels on the A scale. Subjectively, it’s somewhere between a fan and a vacuum. Some people prefer to put NBC filtration systems in a mechanical room to limit the noise, but they need to be in the same air space as the occupants. If it’s in a mechanical room, a louvered vent will ensure it’s in the same air space while reducing the noise.
Very easy, it just bolts together. Once the 4″ penetration hole is made through the wall or ceiling, follow these are steps:
- Take all of the components out of the boxes – everything is labeled and there are carton contents labels on the inside flap of every box.
- Take the shipping bolts off of the Safe Cell and remove the top end bell. The HEPA filter will be exposed – be careful not to damage the pleats.
- Remove the wrapping from the carbon adsorber and set it on the HEPA filter.
- Place the top end bell on the carbon adsorber and install the side plates. You will need two 9/16″ wrenches – crescent or socket wrenches will work just as well.
- Assemble the wall mount kit and bolt it to the Safe Cell using the same wrenches.
- Place the Safe Cell against the wall to locate where the wedge anchors or lag bolts go.
- Remove the Safe Cell and install the wedge anchors or lag bolts.
- Attach the intake hose to the bottom port.
- Install the power cords into the control panel and plug in the AC power cord and attach the DC power cord to your battery.
- Test the Safe Cell by turning on the main power switch and the blower switch.
Be sure and see the manuals for the 60 CFM and 120 CFM Safe Cells for complete installation instructions.
The 60 and 120 CFM manuals have the exact dimensions of the Safe Cells in them, but if you are installing the complete systems that also have the automatic ventilation blower and hand crank, you should budget four feet of wall space with a depth of two feet.
The Safe Cell is an emergency device that should only be used when there is an imminent airborne threat. Once you have your Safe Cell installed and tested, you should keep it sealed up with the shipping caps on the intake and outflow ports when not in use. This will keep the carbon from adsorbing the water vapor in the atmosphere.
We rate our filters at “one event.” If you have nuclear, biological, or chemical event in your neighborhood and you turn on your Safe Cell, you need to change the filters as soon as you get the all clear.
The particulate filters (the pre-filters and the HEPA filter) actually filter more effectively as they load up. We’ve tested our filters with 14 pounds of smoke particulates and they had almost no effect on the airflow.
To ensure the particulate filters last as long as possible, we designed the bottom end bell to have the proper standoff depth so the airflow is diffused and hits the filters over their entire surface. The airflow needs distance to slow down and spread out as it goes from the 4 inch round intake port (12 square inches) to the 12 inch square HEPA filter (144 square inches).
The carbon adsorber attracts and traps gases, molecule by molecule onto the surface of the carbon. Water vapor is one of the gases the carbon adsorbs. Because of this, we recommend keeping the Safe Cell sealed with the shipping caps when not in use so that the performance of the carbon is not degraded by adsorbing water vapor from the atmosphere.
If not used and kept in the original packaging in a climate controlled environment, we recommend replacing the HEPA after six years and the carbon adsorber after three years. See our replacement filter page for more information.
One more note on replacement filters: after the nuclear incident in Japan in 2011, we were sold out of filters within a couple of days. If there is a nuclear event anywhere in the world, we will probably be back ordered on Safe Cells and replacement filters. Every Safe Cell installation should have a complete set of replacement filters.
The automatic ventilation blower is a separate blower that use the same ventilation pipes and intake hose as the Safe Cell to provide unfiltered fresh air ventilation for your shelter. You take the flexible air intake hose off the Safe Cell and attach it to the automatic ventilation blower. There is no scenario where you would need both of them at the same time. You either need filtered air, or you don’t. When there is no threat outside, you leave the intake hose hooked to the automatic blower and set the timer to turn it on every day to keep the air in your shelter fresh and remove condensation.
When there is a threat outside and you go into your shelter, you remove the shipping caps on the Safe Cell and take the intake hose off the automatic ventilation blower and put it on the intake port of the Safe Cell. The hose ends have quick disconnect slip fit so it takes very little time to do this. You can hold your breath while you move the intake hose and hit the on button.
Other air filtration systems (Beth El, Andair, Lunor, and Temet) have a “fresh air” mode where they bypass the filter cartridge and bring in unfiltered air. This put hours on the same blower that the filtration system uses. You may need those hours in during an NBC event. The separate automatic ventilation blower is easily replaceable and does not put any hours on the blower inside the Safe Cell.
Our NBC air filtration systems have been determined to be a munition and subject to export restrictions so we cannot ship them out of the United States.
Even with an export license, we cannot export them for civilian use. Other countries like Switzerland and Israel that have a tradition of civilian bomb shelters have laws that allow for exporting their filtration systems.
The US laws are very clear. There are chemical and biological agents in The United States Munitions Lists. If you build a filtration system that is effective against them, it is considered a munition and the export is controlled.