Protected Floor Space — Air Filtration System

The air filtration system of the protected floor space is the unit that supplies clean, filtered air into the protected space during an emergency, and prevents the penetration of gases, toxins and dust from the outside inward. Its importance stems from the fact that when the occupants are shut inside the protected floor space with a sealed door and window, the filtration system is the only source of safe breathing air — and without a functioning system, the protection of the protected floor space is not complete.

Want to understand how the inspection of the protected floor space filtration system fits into an orderly preventive-maintenance program for the building? Read the complete PPM guide — the process, the matrix and the inspection frequencies for every system in the building.

How the System Works

The protected floor space air filtration system is built from several components working together: a manual or electric supply blower, a filter array (including a coarse filter for dust and a dedicated NBC filter for filtering chemical, biological and nuclear substances), check valves and dampers, and air supply and exhaust openings. In routine times the space serves as an ordinary room, and the filtration system is in a standby state. In an emergency, when the sealed blast door and window are closed, the system is activated to supply clean air.

The operating principle is based on two complementary mechanisms. The first is filtration: the blower draws air from the outside and passes it through the filter array, so that the air coming inside is clean of dust, toxic gases and dangerous particles. The second is over-pressure: the system supplies more air inward than leaks outward, so that a pressure slightly higher than the surroundings is created inside the protected floor space. The over-pressure pushes air out through every crack, thereby preventing from the outset the penetration of unfiltered air through gaps in the door, window or walls.

Unlike an ordinary air-conditioning and ventilation system, which is intended for thermal comfort and ongoing air exchange, the protected floor space filtration system is a protection system whose role is to come into operation at the moment of truth. For that reason its reliability is measured not by daily performance but by its ability to operate exactly when needed — after months or years of non-use.

Why the System Is Needed + Risks of Neglect

The protected floor space was designed to provide protected shelter in an emergency, and when the sealed door and window are closed the space becomes an almost airtight enclosure. Without fresh, filtered air, the internal air runs out, the carbon dioxide level rises, and prolonged occupancy becomes dangerous in its own right — even before an external threat of gas or toxin. The filtration system is what allows staying in the protected floor space over time safely, even when there is contamination outside.

Neglecting the system is especially dangerous because it is "dormant": the system does not operate day-to-day, and therefore a fault in it is not felt — an aged filter, a jammed blower, a sealed check valve or a hardened seal will remain hidden from sight until the moment of activation in an emergency, when it is already too late to repair. An expired NBC filter, for example, may look perfectly sound but fail to provide the filtration for which it was installed. Beyond the safety aspect, verifying the soundness of the filtration system is part of the maintenance of the protected floor space according to Home Front Command guidelines, and the absence of a valid inspection certificate impairs the fitness of the protected space and exposes the building manager and the property owners to liability.

The Maintenance Regime — What, How Often, and How

According to the preventive-maintenance matrix, the inspection of the "protected floor space — air filtration system" is performed at an annual (once a year) frequency, and it applies to every site where there is a protected floor space with a filtration system. The inspection usually includes verifying the soundness of the blower and the activation mechanism, examining the condition of the filter array and replacing filters that have reached the end of their life, checking the check valves and the dampers, and verifying that the system is capable of producing the required over-pressure. Since the system does not operate routinely, the annual inspection is almost the only opportunity to verify that it will indeed work in an emergency.

It is important to note that the filters, and especially the NBC filter, are consumable items with a defined service life: they must be replaced in accordance with the manufacturer's guidance and the current authority guidance, even when they appear sound. In addition, it is recommended that the maintenance team be familiar with the system's operating procedure and practice it as part of the building's emergency procedures — so that at the moment of truth the knowledge does not depend on a single person alone. The exact frequencies for all the building systems can be seen in the matrix in the PPM guide.

Who Is Authorized to Maintain and Certify

The inspection and certification of the protected floor space air filtration system are performed by a maintenance company authorized by the equipment manufacturer. It is not enough to rely on a self-inspection by the maintenance team: this is a dedicated protection system, whose calibration, filter replacement and performance verification require a party that has been explicitly certified by the manufacturer of the installed system, in accordance with the current manufacturer and authority guidance. The authorized party is the one who signs the inspection certificate for each protected floor space separately. A distinction must be made between the inspection of this system and the inspection of the structure of the protected floor space itself (airtightness, blast door and window), which is within the domain of the Home Front Command.

Standards and Regulation

The protected floor space is part of the civil-protection array in Israel, and the design of the protected space, the filtration system and its operation are set according to Home Front Command guidelines and the current standard. In the preventive-maintenance matrix the inspection of the filtration system is classified as a recommended inspection (and not as a separate statutory requirement), but it is an integral part of maintaining the fitness of the protected space. The design of the filters, the airflow rate and the required over-pressure level are set according to the authority and manufacturer guidance — one must not rely on a standard number, threshold value or filter service life that does not appear explicitly in the system documentation and the current Home Front Command guidance.

Required Documentation and Forms

The binding document for the building file is the filtration-system inspection certificate for each protected floor space, issued by the authorized maintenance company at each annual inspection. When a building has several protected floor spaces, a separate certificate is required for each — one general certificate is not sufficient. It is recommended to keep, alongside the certificate, documentation of the filter replacements and their expiration dates, in order to track when each filter (and especially the NBC filter) must be replaced. The protected floor space filtration system has no dedicated fire-service form, and therefore the maintenance company's certificate and the filter documentation are the central documentation to keep and present in an audit.

Common Faults and Warning Signs

From the field, these are the signs the maintenance team should watch for:

• An expired filter — the NBC filter and the consumable filters reach the end of their life according to the manufacturer's guidance; after that date they must be replaced even if they appear perfectly sound.
• A blower that does not spin or a handle that has jammed — an activation mechanism that has not been checked for long months may jam; if the blower does not come up, there is no air supply and no over-pressure.
• Stuck check valves and dampers — a valve that has sealed shut or does not close properly impairs the directionality of the airflow and the ability to create over-pressure.
• Seals that have hardened or cracked — the seals of the door, the window and the system's passages lose flexibility over time; a damaged seal means a leak that prevents the creation of over-pressure.
• Blockage or change of use of the space — when the protected floor space serves as a storeroom and the supply or exhaust openings are blocked by equipment, the system will not be able to operate in an emergency.
• Absence of documentation or an expired certificate — a clear sign that the annual inspection was not performed, and that the system's condition is unknown.

The Value of Professional Maintenance Management / How Domera Helps

The protected floor space filtration system is a clear example of a system that is easy to "forget": it does not operate day-to-day, it has no prominent indication, and its annual frequency comes around only once a year — so that the inspection date easily passes, and an expired filter stays in place, without anyone noticing. This is where orderly maintenance management comes in. Domera manages a preventive-maintenance program for each protected floor space with one open instance at any given moment, closes each inspection only against the certifying document (the filtration inspection certificate for that protected floor space), sends a reminder before the certificate or the filters' validity expires, and centralizes a compliance report that shows at once which protected spaces are fit and which require attention — so that the system meant to protect the occupants is truly ready for the moment of truth.

Frequently Asked Questions

What is a protected floor space air filtration system and why is it important?

This is the system that supplies clean, filtered air into the protected floor space during an emergency, and prevents the penetration of gases, toxins and dust. It is important because when the door and window of the protected floor space are sealed and closed, the filtration system is the only source of safe breathing air — without it the protection of the protected floor space is not complete.

How often is the protected floor space filtration system inspected?

An annual inspection — once a year — by a maintenance company authorized by the equipment manufacturer, in accordance with the preventive-maintenance matrix.

Who is authorized to inspect and certify?

A maintenance company that has been explicitly certified by the equipment manufacturer. The internal maintenance team is not authorized to sign the inspection certificate of the filtration system.

What is over-pressure in a protected floor space?

The system supplies more filtered air inward than leaks outward, so that a pressure slightly higher than the surroundings is created inside the protected floor space. The over-pressure pushes air out through every crack, thereby preventing from the outset the penetration of unfiltered air through gaps in the door, window or walls.

What is the role of the NBC filter?

The NBC filter is intended to filter chemical, biological and nuclear substances from the incoming air. It is a consumable item with a defined service life, and it must be replaced according to the manufacturer and authority guidance even if it appears sound.

What is the difference between the protected floor space filtration system and ordinary air conditioning?

Ordinary air conditioning and ventilation is intended for thermal comfort and ongoing air exchange in routine times; the protected floor space filtration system is a protection system that comes into operation in an emergency to supply clean air and prevent the penetration of toxins. These are two separate systems with a different purpose.

What documentation must be kept in the building file?

The filtration-system inspection certificate for each protected floor space, issued at each annual inspection by the authorized maintenance company. In a building with several protected floor spaces, a separate certificate is required for each, and it is recommended to also keep documentation of the filter replacements and their expiration dates.

Is the inspection a legal requirement?

In the preventive-maintenance matrix the inspection is classified as recommended and not as a separate statutory requirement, but it is an integral part of maintaining the fitness of the protected space in accordance with Home Front Command guidelines. The absence of a valid certificate impairs the fitness of the protected floor space.

Further Reading

• Air-conditioning and ventilation system maintenance — the difference between air conditioning for ongoing comfort and the protected floor space filtration system, which is a protection system for emergencies.
• Emergency procedures in an office building — how activating the filtration system and staying in the protected floor space fit into overall emergency preparedness.
• The complete PPM guide — the preventive-maintenance process and the frequency matrix for all the building systems.
• Domera Knowledge Hub — all the guides and articles on building management and maintenance.