Hazards to be aware of and preventive measures when using gas fire suppression systems

　　As a form of fire suppression, gas-based firefighting is widely used in the market due to its outstanding performance and high extinguishing efficiency. However, since gas fire suppression systems are essentially chemical products, it’s only natural that they also pose certain risks. Yet, we must not overlook the two major sources of danger associated with these systems. Today, we’ll highlight the two key hazards that users should be aware of when operating gas-based fire suppression equipment. Of course, as long as we rely on equipment manufactured by reputable, authorized manufacturers, there’s no need to worry about safety concerns.

　　These two major hazards are: first, the risk of gas overpressure; and second, the risks of asphyxiation and toxicity.

　　The building must meet at least a Class II fire resistance rating, and according to relevant regulations, storage areas for pressure vessels must have direct access either to the outdoors or to evacuation corridor exits. Additionally, the ambient temperature in bottle rooms and protected zones equipped with prefabricated fire suppression systems should be maintained between -10°C and 50°C, while the ambient temperature for storage units of high-pressure carbon dioxide fire-extinguishing systems must remain within the range of 0°C to 49°C.

　　I. Risks of Gas Overpressure and Preventive Measures:

　　1. During the use of gas cylinders, the cylinder body is subjected to prolonged pressure and may be affected in its pressure-bearing capacity due to external contamination and the internal medium.

　　2. Gas cylinders must be inspected strictly according to relevant standards. Steel cylinders that have reached their service life limit must be scrapped, in compliance with the provisions of the "Safety Technical Supervision Regulations for Gas Cylinders" (TSG R0006-2014). The regulations also specify detailed requirements regarding cylinder markings (steel stamping), service life limits, periodic inspection intervals, inspection labels, and qualification criteria.

　　3. Safety regulations for handling, loading, unloading, storing, and using gas cylinders can be referred to the relevant provisions of "Safety Regulations for Handling, Loading, Unloading, Storing, and Using Gas Cylinders" (GB/T 34525-2017).

　　4. The pressurization pressure of prefabricated fire suppression systems installed within the protected area should not exceed 2.5 MPa.

　　5. For IG541 mixed-gas fire suppression systems and other similar systems, the storage units are maintained under long-term high-pressure conditions. Therefore, the cylinder room must meet not only the general requirements for cylinder rooms but also comply with national regulations governing the storage of high-pressure vessels.

　　6. When the combined distribution system is activated, the selector valve should open either before or simultaneously with the container valve.

　　7. The storage units for pipeline-based fire suppression systems should ideally be located in a dedicated cylinder room, which is situated close to the protected area.

　　8. The arrangement of storage equipment should facilitate operation and maintenance, while also preventing direct sunlight exposure. The distance from the operating surface to the wall or between two operating surfaces must be no less than 1.0 meter, and also no less than 1.5 times the outer diameter of the storage containers.

　　Second, suffocation and toxicity risks, along with corresponding preventive measures:

　　1. Among all gaseous fire suppressants, carbon dioxide poses the highest safety risk, primarily due to its asphyxiation hazard. When the concentration of carbon dioxide exceeds 10%, it can cause human unconsciousness. However, the design concentration of carbon dioxide-based fire suppression systems is typically set at least above 34%. Therefore, carbon dioxide total flooding systems are not recommended for use in areas where people may be present. In particular, carbon dioxide should never be used in spaces like basements, as it is heavier than air, which would further complicate ventilation and air exchange after discharge.

　　2. Typically, the fire suppression design concentrations of Heptafluoropropane and IG541 do not exceed the NOAEL concentration, and at reasonable levels, neither Heptafluoropropane nor IG541 pose any toxicity or asphyxiation risks.

　　Design and construction personnel must thoroughly understand the non-toxic and toxic reaction concentration requirements for gaseous fire suppressants. In protected areas where people are present, the actual extinguishing concentration used should not exceed the toxic reaction concentration.

　　3. The protected area shall have passages and exits that ensure personnel can evacuate completely within 30 seconds.

　　4. Emergency lighting and evacuation direction signs shall be installed along evacuation routes and at exits within the protected area. Fire alarm sounders should be designed throughout the protected area, with strobe alarms optionally added when necessary. At the entrance to the protected area, install fire alarm sound and light devices, extinguishing agent discharge indicator lights, and signage indicating that the area is equipped with the corresponding gas-based fire suppression system. The extinguishing agent discharge indicator light signal will remain active until the protected area has been adequately ventilated and manually reset.

　　5. Doors in the protected area should open in the direction of evacuation and be capable of self-closing; however, doors primarily used for evacuation must be operable from inside the protected area.

　　6. After fire suppression, the protected area should be ventilated. For underground protected areas and above-ground protected areas without windows or equipped with fixed window panels, mechanical exhaust systems must be installed, with exhaust vents positioned at the lower part of the protected area directly leading outdoors. In spaces such as communication equipment rooms and electronic computer rooms, the ventilation rate should be no less than 5 air changes per hour.

　　7. Manual control and emergency operations of the fire suppression system should be equipped with warning displays and measures to prevent accidental activation.

　　8. In areas equipped with gas fire suppression systems, it is advisable to provide air respirators.

　　9. For total flooding carbon dioxide fire suppression systems, gas-based fire protection zones where the other design concentration or actual usage concentration exceeds the non-toxicity reaction concentration shall be equipped with a manual-to-automatic control switching device. When personnel enter the protected zone, the system can be switched to manual control mode; upon their departure, it automatically reverts back to automatic control mode. Additionally, display devices indicating the current manual or automatic control status should be installed both inside and outside the protected zone.

　　10. When using the automatic control start-up method, a controllable delay of no more than 30 seconds shall be provided to ensure personnel can safely evacuate the protected area. For protected areas that are normally unoccupied, the system shall be set to deliver an immediate, non-delayed discharge.

　　11. The door of the cylinder room should open outward, and emergency lighting must be installed inside the cylinder room. The cylinder room should also have adequate ventilation; for underground cylinder rooms, a mechanical exhaust system is required, with exhaust vents positioned at the lower level to allow air to be expelled outdoors via exhaust ducts.

　　12. For storage compartments of carbon dioxide fire suppression systems that lack natural ventilation, mechanical exhaust systems must be installed. The exhaust outlet, when located no more than 0.5 meters above the floor of the storage compartment, should lead directly outdoors. The normal exhaust volume should be determined based on an air exchange rate of at least 4 times per hour, while the emergency exhaust volume must be calculated using an air exchange rate of no less than 8 times per hour.