Mamad NBC Air Filtration System — Types, Installation & Maintenance

What Is an NBC Filtration System?

An NBC (Nuclear, Biological, Chemical) filtration system filters the air entering a mamad safe room and protects occupants from toxic airborne agents. The system creates positive pressure inside the room — meaning the air pressure inside is higher than outside, so even if there are small gaps in the seal, air flows outward rather than inward.

According to Israeli Standard 4910 and Home Front Command guidelines, every mamad must include a functioning NBC filtration system ready for use.

Types of Filtration Systems

Disposable Filter (Standard)

• Use: Single-use, up to 48 continuous hours
• Filtration: Particles, toxic gases, biological agents
• Weight: 5-8 kg
• Price: 800-1,500 NIS
• Shelf life: Up to 10 years in sealed packaging

This is the most common filter in residential mamads. It comes as a sealed unit that connects to the mamad’s air duct.

Reusable Filter (Professional)

• Use: Reusable with replaceable cartridges
• Filtration: Same as disposable, but with replaceable components
• Weight: 10-15 kg
• Price: 2,000-4,000 NIS
• Shelf life: Frame — unlimited; cartridges — 10 years

Suitable for institutions, public shelters, and upgraded mamads.

Powered Filter with Electric Blower

• Use: Creates active positive pressure
• Capacity: 15-25 cubic meters per hour
• Price: 3,000-6,000 NIS
• Requires: Electricity or battery

A premium system that ensures constant positive pressure and allows extended stays in the mamad.

Step-by-Step Installation Guide

Important: Installing a new filtration system from scratch should be performed by a certified professional. The following steps are for general understanding and for replacing an existing filter.

Step 1: Check the Infrastructure

1. Locate the filtration port in the mamad wall — typically a round duct, 4 inches in diameter, in the exterior wall.
2. Verify the duct is open and not blocked from inside or outside.
3. Check that the rubber gasket around the duct is intact.
4. Confirm there is an electrical outlet nearby (for systems with a blower).

Step 2: Remove the Old Filter

1. Release the locking clips on the old filter (usually 2-4 clips).
2. Carefully pull the filter out of the duct.
3. Inspect the duct’s rubber gasket — replace it if dry or cracked.
4. Clean the inside of the duct with a cloth and vacuum.

Step 3: Install the New Filter

1. Remove the new filter from its sealed packaging — only when you are ready to install.
2. Verify the expiration date has not passed.
3. Insert the filter into the duct in the correct orientation (airflow arrow pointing inward).
4. Secure the locking clips until you hear a “click.”
5. Verify there are no gaps between the filter and the duct wall.

Step 4: Test for Proper Function

1. Close all openings in the mamad — door, window, and ventilation port.
2. Light a candle or match near the door frame — the flame should lean outward (indicating positive pressure).
3. Verify air is flowing through the filter and not around it.
4. If the system has a blower, turn it on and confirm it runs quietly and smoothly.

Step 5: Document and Label

1. Write the installation date on the filter.
2. Note the expiration date in a visible location.
3. Keep the manufacturer’s instructions inside the mamad.

Maintenance Schedule

Task	Frequency	Notes
Visual inspection of the filter	Every 6 months	Look for moisture, rust, damage
Check expiration date	Once a year	Replace before expiration
Inspect rubber gaskets	Once a year	Dry rubber means no seal
Clean the filtration duct	Once a year	Remove dust and debris
Test positive pressure	Once a year	Candle/match test
Replace filter	Every 10 years	Or per expiration date

When to DIY vs. When to Call a Professional

Task	DIY?	Notes
Visual inspection	Yes	Basic maintenance
Duct cleaning	Yes	Damp cloth and vacuum
Disposable filter replacement	Yes	Simple removal and insertion
Rubber gasket replacement	Yes	Similar to window seal replacement
New system installation from scratch	No	Requires a certified installer
Electric blower repair	No	Requires a licensed electrician
Drilling a new filtration duct	No	Professional concrete work

Price Guide 2026

Item / Service	Estimated Price
Disposable filter	800-1,500 NIS
Reusable filter	2,000-4,000 NIS
Powered system with electric blower	3,000-6,000 NIS
Replacement cartridge (reusable)	600-1,200 NIS
New system installation (including labor)	1,500-3,000 NIS
Blower repair/replacement	500-1,500 NIS
Filtration duct gasket replacement	100-300 NIS

Important Tips

• Do not open the filter packaging until you are ready to install. A filter exposed to air begins to degrade.
• Per Home Front Command guidelines, verify that the filtration system is functional and has not expired.
• Keep a sealed backup filter if the installed one is nearing its expiration date.
• During an emergency, close the door and window first, then activate the filtration system.
• Israeli Standard 4910 defines the minimum filtration requirements. Ensure the filter you purchase meets the standard.

FAQ

Does the filter work without electricity? Disposable and basic reusable filters work without electricity — they are passive and rely on pressure differentials. Powered systems with an electric blower require electricity or a backup battery.

How long does the filter last during an event? A disposable filter is designed for up to 48 continuous hours. A reusable filter depends on the cartridge, typically 48-72 hours.

Do I need to replace a filter that was never used? Yes. Even a sealed filter has an expiration date (usually 10 years from the manufacturing date). Once opened, it must be installed immediately.