SHX-UN
Universal pressure relief vent for Inert Gas
Product details
- Largest verified Free Vent Area (FVA) on the market.
- Single direction venting for positive pressure.
- Applicable with gas fire suppression systems using inert gases.
- Operates at 80 Pascals and fully open at 95 Pascals.
- Available in 4 standard sizes.
- Can be adapted for ceiling mounted applications.
- Constructed from Steel Zintec and powder coated with RAL 9003 white.
- 5 year warranty.
- Available off the shelf on next day delivery.
- For exterior walls less than 140 mm thick, a Z frame is required to fit a DWL weather louvre.
Kit: The kit includes a wall liner, wall liner extension and fitting kit. The standard kit can be installed into walls up to 380 mm. For thicker walls, additional wall liner extensions are required.
Note: This product is not suitable for external coastal environments, as it will cause rust. For coastal environments, the SHX-UN Stainless Steel should be used.
SHX-UN universal pressure relief vent
The SHX-UN Universal Pressure Relief Vent is an advanced solution for blast protection and gas suppression pressure relief, designed for use with all inert gases. Featuring a patented design, it offers the largest verified Free Vent Area (FVA) on the market. It makes these universal inert gas vents highly effective for overpressure relief and is also capable of handling high-energy blasts, such as those found in electrical switchgear and transformer installations.
The SHX-UN stands out as the only vent with its FVA independently verified to the BRE Live Discharge Test (122084). Its performance is further enhanced by a vent dynamic coefficient (vDc) of 1.15 for gas suppression scenarios, ensuring precise performance during critical events. Additionally, the SHX-UN is discharge-tested for cascade venting scenarios and operates efficiently at 80 Pascals, fully opening at 95 Pascals.
To adapt to various installation requirements, the SHX-UN offers an optional weather louvre and security grilles for external wall installations, providing protection against the elements and unauthorized access. A Z-frame is also available, making it easy to install the vent in thin walls while maintaining its full functionality and structural integrity.
For large-scale suppression systems, the vent can be used alongside our BSV IN Insulated Blast Vent or BSV F-INS Blast Vent with Fire Rated Insulation
A legacy of innovation
The SHX-UN builds on years of evolution in AFP's pressure venting technology. Introduced in 2008, it refines the earlier HXD design, which revolutionized the industry by replacing inefficient bottom-weighted blades with lightweight, double-skinned louvre blades and offset pivot points. These innovations greatly improved performance, ensuring reliable closure at low pressures while handling peak pressures of 250 to 500 Pascals in gas suppression systems.
The SHX-UN further enhances this legacy with unique features, including a top weight for blade balance and curved, interlocking blade edges for maximum efficiency. These advancements allow the vent to achieve 100% of its Free Vent Area at very low pressures, offering unmatched performance in demanding environments.
Proven performance
All SHX-UN pressure vents are rigorously tested in-house using AFP's proprietary equipment and protocols, meeting the standards of the BRE Live Discharge Test. This testing method records the exact movement of vent blades over time, proving the vent’s FVA (0.067 m² at 96 Pa for SHX-UN300) and enabling accurate predictions of back pressure and peak pressure during live scenarios. Unlike standard HVAC testing, which holds blades open or relies on constant airflow, the SHX-UN is tested under real-world conditions, ensuring dependable performance in critical applications.
These are the test results from a test performed in a 43m3 steel container. Compressed air was discharged into the container. With the linkage that connects all the blades, the blade opening could be measured. The pressure in the container raised < 0.01 Pa due to air pressure relief with the SHX-UN.
Certifications & testing
- 4 Hour Fire Resistance rated by Exova to BS EN 1363-1 and BS EN 1364-1.
- Live discharge test 122084, including vent area validation, certified by BRE.
- Blast and Explosion tested with AFP's blast simulator.
- Blast test review by BRE.
- Pressure tested for room leakage by Pressure test
Types of gases
The SHX-UN can be used with gaseous fire suppression systems using any inert gas. Inert gases are non-reactive and leave no residue, making them ideal for protecting sensitive equipment and critical spaces. Inert gaseous agents include:
- Nitrogen (N₂)
- Argon (Ar)
- Carbon Dioxide (CO₂)
- Inergen® (Blend of N₂, Ar, and CO₂): IG-55, IG-100, IG-541
- Argonite® (Blend of N₂ and Ar)
Benefits of certification
Testing and certification are essential to ensure that products meet strict safety and performance standards. In real-life applications, this means that certified vents, like the SHX-UN, reliably perform in extreme conditions such as gas discharges, blasts, or fires, significantly reducing the risk to personnel. Certification to standards such as the BRE Live Discharge Test ensures that the vents are compatible with industry gas calculation software models. This allows for precise performance predictions and preventing dangerous over-pressurisation during a live gas discharge — mitigating the risk of blockage and ensuring safe operation.
Fire testing guarantees that the vents act as an effective fire barrier when installed in a block wall, providing essential protection in high-risk environments. Extensive blast resistance testing proves their ability to withstand extreme pressures, preventing structural damage and safeguarding the integrity of the enclosure. By undergoing thorough certification, the SHX-UN vent ensures consistent and reliable performance when it matters most, offering peace of mind in critical situations.
Integrity testing calibration
The AFP range of universal pressure relief vents do not require calibration from an integrity test, as they are fully certified to the BRE Live Discharge test of 2008 (room leakage 3,43 cm3 for SHX-UN-500).
Get in touch
Get in touch for a quote, more information, assistance with correct sizing, or bespoke solutions tailored to your needs.
Product operation video
In the video below is explained how the SHX-UN pressure relief vent regulates the room pressure by opening when positive pressure builds up after a gas release, allowing excess air to escape. Once the room pressure stabalizes, the vents close automatically to maintain room integrity.
Unit selection
The SHX-UN pressure relief vents are offered in a number of standard sizes for installation in both internal and external walls.
| Product Code | SHX-UN300 | SHX-UN500 | SHX-UN700 | SHX-UN1000 |
| Free Vent Area | 0.077m2 | 0.212m2 | 0.416m2 | 0.85m2 |
| Overall WxHxD | 420x420x120mm | 620x620x120mm | 820x820x120mm | 1120x1120x120mm |
| Hole cut out WxH | 360x350mm | 560x550mm | 760x750mm | 1060x1050mm |
| Leakage (3% of FVA) | 0.0023m2 | 0.0063m2 | 0.0121m2 | 0.038m2 |
| Wall Mounted Weight | 12kg | 19kg | 34kg | 53kg |
| Ceiling Mounted Weight | 11.5kg | 17.5kg | 30.5kg | 44kg |
Add-ons
DWL
Dynamic Weather Louvre offering superior wind and weather protection for external walls, without restricting the internal vents Free Vent Area (FVA).
Grilles
The AFP product range offers several security grilles to mount on vents in outside walls for different levels of protection.
Z-Frame
Powder coated steel stub duct for mounting the SHX-UN into thin walls, doors, and cladding of less than 100 mm thick.
Wall liner
A wall liner is an extension for internal wall depths that exceed 15" thickness. With extra wall liners, minimal leakage and FVA will still be applicable.
Downloads
Access detailed technical information on the SHX-UN, including data sheets, installation guides, and technical drawings, by downloading the resources below.
Get in touch
Get in touch for a quote, more information, assistance with correct sizing, or bespoke solutions tailored to your needs.
Related products
SHX-UN MOT
SHX-OS
DUX
