Pressure relief venting for chemical gas fire suppression systems
Note: This page covers pressure relief vents for chemical gas fire suppression systems.
If you’re unsure whether your system uses inert or chemical gas, start with our Choose Your Vent Guide to find the right solution.
When a chemical gas fire suppression system discharges, it does more than extinguish flames. It creates a rapid increase in pressure inside the protected room. Without proper venting, that sudden pressure spike can damage walls, ceilings, doors, or critical equipment. That’s where pressure relief vents come in.
Designed specifically for use with chemical clean agent systems like FM-200, NOVEC 1230, or similar agents, these vents help maintain room integrity during discharge by allowing excess pressure to safely escape. They protect both the building structure and the fire suppression system’s effectiveness.
This article explains why venting is important in chemical gas suppression design. It shows how venting works. It also tells you what to think about when picking the right vent for your use.
What is a chemical gas fire suppression system?
A chemical gas fire suppression system is a specialized fire protection solution that uses clean agent gases to quickly extinguish fires without damaging sensitive equipment or leaving residue behind.
Unlike traditional sprinkler systems that use water, these systems release a chemical gas, also known as a clean agent. This gas either disrupts the fire’s chemical reaction or cools the area to extinguish the flames quickly.
Chemical gas systems are clean, non-conductive, and safe for electrical equipment. This makes them ideal for protecting areas where water damage from sprinkler systems could be expensive or harmful.
Typical applications include:
- Data centers and server rooms
- Telecommunication facilities
- Control rooms and electrical switchgear rooms
- Laboratories and clean rooms
- Museums and archives
- Medical facilities and operating rooms
- Industrial process control areas
Common chemical gases
In clean agent fire suppression systems, the following gaseous suppression agents are commonly used:
- HFC-227ea (FM-200)
- FK-5-1-12 (NOVEC 1230)
- HFC-125
- HCFC Blend (e.g., FE-13)
These gases are stored in cylinders as liquids or compressed gases and rapidly released into the protected area when the system activates.
While they are safe for sensitive equipment and leave no residue, the sudden discharge can cause a rapid pressure increase in the room, which must be managed carefully to prevent structural damage.
What happens when chemical gases discharge?
When chemical gas fire suppression agents are released, they cause a distinct pressure behavior inside the protected room. As the agent rapidly evaporates, its heat absorption cools the surrounding air significantly. Since cooler air occupies less volume than warm air, this sudden temperature drop causes the air inside the room to contract quickly.
This rapid contraction creates negative pressure inside the space, producing a vacuum effect. Negative pressure pulls inward on walls, windows, and doors, which can place stress on the room’s structure and potentially cause damage if not properly managed.
After the discharge and cooling phase, the air inside the room gradually warms back to its original temperature. As the air warms, it expands, causing a rise in pressure above atmospheric levels. This positive pressure phase follows the initial negative pressure, resulting in a pressure cycle with both drops and spikes.
To protect the room’s structural integrity throughout this cycle, pressure relief vents must be designed to accommodate both negative and positive pressure changes. Proper venting ensures that the building and contents remain safe while maintaining the effectiveness of the fire suppression system.
Carbon dioxide
Unlike agents such as FM-200™ or NOVEC™ 1230, carbon dioxide behaves somewhat differently. When CO₂ systems are activated, they rapidly expand and increase room pressure without the same significant cooling effect. This typically results in a dominant positive pressure rise with less pronounced negative pressure. However, the pressure changes can still be substantial and require appropriate venting solutions to protect the room structure.
What is pressure relief?
Pressure relief is a safety measure used to protect enclosed spaces from damage caused by sudden changes in internal pressure. In the context of chemical gas fire suppression systems, pressure relief refers to the controlled venting of excess pressure that builds up inside a room when the fire suppression agent is discharged.
Pressure relief vents are specially designed openings that automatically open at a predetermined pressure threshold, allowing air or gas to flow in or out of the room. This venting prevents excessive pressure buildup or vacuum conditions by equalizing the pressure inside the room with the outside atmosphere.
In essence, pressure relief protects both the building structure and the integrity of the fire suppression system, ensuring the space remains safe and operational after an agent discharge.
Key features of pressure relief systems for chemical gas
Proper pressure relief is essential to protect the room’s structure while maintaining the correct concentration of chemical agent needed for effective fire suppression. Key features of pressure relief systems designed for chemical gas include:
- Fast response. Vents must open quickly to accommodate both the rapid negative and positive pressure changes during discharge.
- Leak-tight seal. When inactive, vents need to remain completely sealed to preserve the room’s airtight environment and prevent loss of the clean agent.
- Bi-directional pressure management. Because chemical gas systems experience both negative (vacuum) and positive (overpressure) phases, vents must be capable of relieving pressure in both directions.
- Durability. Pressure relief vents must endure multiple discharges, resist environmental factors, and maintain reliable operation over time.
Choosing the right venting solution for chemical gas fire suppression systems
Not all pressure relief vents are suitable for chemical gas systems. Because chemical agents create a unique pressure cycle with both negative and positive pressure phases during discharge, the venting solution must be specifically designed to manage these conditions effectively.
What to consider when selecting a vent
Selecting the right vent for a chemical gas fire suppression system goes beyond size and location. It’s about how well the vent responds to the dynamic pressure changes caused by the agent discharge. Key factors to consider include:
- Pressure cycle management. Chemical gas discharges cause rapid shifts from negative to positive pressure. Vents must respond quickly and reliably to both pressure drops and spikes to protect the structure.
- Room size and construction. The size of the protected space and the strength of its enclosure influence the venting area required and the vent’s opening pressure setting.
- Opening pressure. Vents must open at a pressure low enough to prevent structural damage, yet remain sealed during normal conditions to maintain airtightness.
- Resealing ability. After pressure equalization, the vent must close securely to preserve the clean agent concentration and protect against contaminants.
- Installation requirements. Proper placement, orientation, and sealing are crucial to ensure vents perform as designed throughout their service life.
Selecting a high-quality pressure relief vent made for chemical gas systems is essential. It helps maintain room integrity and ensures the fire suppression system works effectively during and after discharge.
DUX: Pressure relief vent designed for chemical gas fire suppression systems
The AFP DUX Pressure Relief Vent is engineered specifically to meet the demanding requirements of chemical gaseous fire suppression systems. It is rigorously tested and certified to perform reliably under rapid pressure fluctuations caused by clean agent discharges, ensuring both safety and room integrity.
The DUX features a precision-balanced, bi-directional design that allows it to respond quickly to both negative and positive pressure changes. Its lightweight mechanism opens smoothly at set pressures and reseals tightly once conditions normalize, maintaining an airtight environment and protecting sensitive equipment.
Key features of the DUX
- Designed for chemical gas systems with bi-directional pressure relief
- Fast, reliable response to both vacuum and overpressure phases
- Adjustable opening pressure for tailored protection
- Leak-tight seal to preserve agent concentration and room airtightness
- Durable construction built to withstand multiple discharges
- Suitable for use in data centers, control rooms, telecommunication facilities, and other sensitive environments
The DUX vent provides peace of mind by ensuring that chemical gas suppression systems operate safely without compromising structural integrity or the effectiveness of the agent discharge.
Vent sizing
Sizing of the vents for risk should be derived and confirmed from either the gas supplier’s calculations or from an integrity test. However, for a rough estimation, please refer to the following charts.
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