Managing air pressure is an essential part of building safety, particularly in facilities that use gaseous fire suppression systems or pressurised escape routes. When pressure rises or falls beyond acceptable limits, it can place unnecessary stress on building components, affect door operation and compromise the intended performance of safety systems.
Pressure relief vents provide a controlled path for air or gas to escape or enter when specified pressure conditions occur. Unlike ordinary ventilation grilles, purpose-designed pressure relief vents respond to pressure differentials and are selected according to the demands of a particular installation.
From commercial buildings and high-rise stairwells to data centres and industrial facilities, selecting the appropriate vent requires careful consideration of opening pressure, airflow capacity, fire resistance and installation requirements.
Understanding Pressure Relief Vents and Their Function
A pressure relief vent is a mechanical device designed to control pressure differences between two spaces.
In many applications, the vent remains closed during normal operating conditions. When the pressure differential reaches a specified level, its blades open to allow airflow and relieve the pressure.
The design helps maintain pressure within the intended operating range.
Engineers specifying Pressure Relief Vents can explore Apreco’s specialist range, which includes solutions for stairwell pressurisation, inert gas fire suppression, synthetic gas systems and data centre applications.
Apreco designs and manufactures its pressure relief vents in the United Kingdom, with different product configurations available to meet the requirements of individual projects.
Why Pressure Relief Is Essential in Fire Suppression Systems
Gaseous fire suppression systems protect sensitive environments where conventional water-based suppression may be unsuitable.
Such environments include data centres, electrical equipment rooms, museums and other facilities containing valuable assets.
When a gaseous suppression system activates, the rapid discharge of extinguishing agent can cause significant changes in room pressure.
Inert gas systems typically create positive pressure during discharge, while some synthetic gas systems can create negative-pressure conditions.
Without appropriately designed pressure relief, these changes may place excessive loads on walls, ceilings, doors and other building components.
A correctly selected pressure relief vent provides an airflow path that helps limit pressure excursions.
The required venting capacity depends on the suppression agent, discharge characteristics, enclosure construction and allowable pressure limits.
Apreco IGV Inert Gas Vents for High-Pressure Fire Suppression
Apreco’s IGV Inert Gas Vent range is specifically designed for over-pressure venting associated with high-pressure inert gas fire suppression systems.
The IGV range provides single-direction venting and is designed to be fully open at a pressure differential of 100 pascals.
According to Apreco’s published product information, key characteristics include:
- Up to four hours of fire resistance tested to BS EN 1634-1.
- BSRIA-validated free vent area.
- Eight standard sizes.
- Single-direction pressure relief.
- Reversible flange arrangements for alternative flow configurations.
- Individual serial-number traceability.
- A standard 10-year warranty.
The reversible flange design provides installation flexibility when the airflow direction must be changed.
This makes the IGV range relevant to projects where controlled pressure relief must be integrated with a gaseous fire suppression system and fire-resistance requirements.
SGV Dual Flo® for Synthetic Gas Fire Suppression
Not all gaseous fire suppression systems generate the same pressure conditions.
Synthetic gas systems may produce pressure changes in both directions during discharge, making bidirectional relief an important design consideration.
Apreco’s SGV Dual Flo® Halocarbon Pressure Relief Vent is designed for synthetic gas fire suppression applications.
Its true two-way venting configuration allows the system to address both positive and negative pressure conditions.
Apreco lists a nominal upward opening pressure of 125 pascals for the SGV range and fire-resistance options of up to three hours.
The SGV Dual Flo® is particularly relevant where a suppression system requires bidirectional pressure management rather than a single-direction vent.
Engineers should confirm the required venting area and pressure response using the appropriate manufacturer performance data.
PRV-F2 Pressure Relief Vents for Stairwell Pressurisation
Pressurised stairwells are designed to help limit smoke entry into escape routes during a fire.
A stairwell pressurisation system introduces air to establish a pressure difference between the protected stairwell and adjacent areas.
However, excessive pressure can make doors difficult to open.
Pressure relief vents help prevent the pressurisation system from exceeding its intended operating limits.
Apreco’s PRV-F2 range is designed for stairwell pressurisation and other industrial applications.
The product has a default pressure setting of 45 pascals and is designed for single-way venting.
It has also undergone a 240-minute fire-resistance test to BS EN 1634-1:2014 + A1:2018.
Apreco publishes several standard PRV-F2 sizes with different airflow capacities.
PRV-F2 Airflow Performance
| Model | Nominal Size | Airflow at 45 Pa | Airflow at 50 Pa |
|---|---|---|---|
| PRV-F2-0303 | 300 × 300 mm | 440 L/s | 465 L/s |
| PRV-F2-0505 | 500 × 500 mm | 1,190 L/s | 1,255 L/s |
| PRV-F2-0707 | 700 × 700 mm | 2,300 L/s | 2,430 L/s |
| PRV-F2-1010 | 1,000 × 1,000 mm | 4,645 L/s | 4,910 L/s |
These published performance figures illustrate why vent sizing must be based on the required airflow at the relevant pressure differential rather than physical dimensions alone.
Ceiling-Mounted Pressure Relief for Data Centres
Data centres require particular attention to pressure management because they often contain sensitive electrical equipment and specialised fire suppression installations.
Pressure changes during a suppression event may affect ceiling systems and other enclosure components.
Apreco offers a ceiling-mounted pressure relief solution designed specifically for data centre applications.
The PRV-F2-C-0510 is a single-direction ceiling-mounted vent with the following operating characteristics:
- Designed to remain closed below 35 pascals.
- Begins opening at approximately 40 pascals.
- Fully open at 50 pascals.
- Alternative opening pressures available on request.
- Bespoke sizes available for different ceiling arrangements.
This controlled opening sequence allows the vent to respond to pressure changes associated with the intended application.
For data centre installations, the vent must be selected alongside the enclosure design and the fire suppression system’s calculated pressure-relief requirements.
Motorised Pressure Relief Vents for Flexible Operation
Some installations require more than passive pressure relief.
For example, an enclosure may need pressure relief during fire suppression while also requiring controlled natural ventilation under other operating conditions.
Apreco’s IGV-M Motorised Inert Gas Vent combines a single-direction pressure relief vent with a motorised actuator.
The actuator enables the blades to open or close for ventilation applications.
Apreco lists the IGV-M as fully open at 100 pascals, with BSRIA free vent area validation and a standard 10-year warranty.
The motorised configuration may be appropriate for cascade venting arrangements or spaces requiring additional ventilation functionality.
Its integration with building controls and fire suppression equipment should be assessed as part of the overall system design.
Key Factors When Selecting a Pressure Relief Vent
Choosing the correct pressure relief vent requires more than matching a product to an opening in a wall.
1. Pressure Differential
The opening pressure must suit the operating requirements of the system.
A vent designed for stairwell pressurisation may have a substantially different operating pressure from one intended for inert gas fire suppression.
2. Required Airflow Capacity
The vent must provide sufficient airflow at the specified pressure differential.
Manufacturer airflow data should be used in conjunction with project-specific calculations.
3. Direction of Pressure Relief
Some systems require positive-pressure relief, while others require negative-pressure or bidirectional relief.
The correct airflow direction is essential for the intended operation.
4. Fire-Resistance Requirements
Where a vent penetrates a fire-resisting wall or enclosure, its tested fire-resistance characteristics and installation configuration must be suitable for the project.
5. Mounting Location
Pressure relief vents may be installed in walls or ceilings, depending on the product and application.
The supporting structure, clearances and installation details should be considered during design.
6. Maintenance and Accessibility
Vent blades and associated components should remain accessible for inspection and maintenance.
Obstructions, damage or unauthorised modifications can affect performance.
The Importance of Testing and Product Documentation
Pressure relief performance should be supported by reliable technical data.
Apreco publishes product-specific information covering operating pressures, vent dimensions, airflow performance and installation requirements.
Several products also include BSRIA free vent area validation.
This information helps engineers assess whether a vent is suitable for the required applicati
