Smoke and Flames rising from residential buildings, hotels and warehouses have become a common sight nowadays. Out of 1.2 million fires reported in the U.S.A in 2013, almost 39% of the cases were structural fires causing more than 2800 deaths and $9.5 billion in property damagei. The `Center for Disease Control and Prevention’ notes death from fires and burns are the fifth most common cause of unintentional injury deaths and third leading cause of fatal home injury. SMOKE inhalation during fire accidents is another major reason for deaths in such cases.
In a case study conducted by NFPA, it was found that the HVAC system was not linked to smoke detector system and did not shut off during fire accident. The air from the operating HVAC system and Natural ventilation increased the growth of the fire. It is therefore important to cutoff air supply by shutting down HVAC system during fire. Various fire safety equipment are prescribed by national authorities in their building codes to overcome fire hazards in order to save life and property. One such requirement is the use of FIRE DAMPERS in the HVAC system.
Fire damper is a device installed in an air distribution system or an air transfer opening designed to close automatically upon detection of heat interrupting airflow and thereby restricting the passage of fire in the process.
Fire dampers are installed in fire rated walls / barriers / partitions where the HVAC ductwork penetrates ensuring that their integrity is maintained. The location and installation procedure of fire dampers should be in accordance with the widely accepted and recommended standard, NFPA 90A — Standard for the installation of Air-Conditioning.
The most prominent testing laboratories for evaluating fire resistive materials and assemblies is the Underwriters Laboratory (UL), U.S.A. All Airmaster Fire dampers are tested and certified by UL.
Airmaster fire dampers are developed with the intention of maximizing the occupant’s safety. There are two basic types of damper operations: a) Curtain type b) Multiple blade type. Though construction of both dampers are different, the purpose is the same —to interrupt airflow in order to restrict the passage of fire & smoke.
Curtain type: The blades are folded and held under spring tension using a bi-metal fusible link. Heat of 165°F (74°C) inside the duct is sufficient for fusible link to melt and break, thus allowing blades to shut like a curtain under the force of the springs attached. The fire damper acts as a barrier between fire and non-fire zones thus containing the fire in the compartment from which it originated. This gives sufficient time for occupants to escape and move into safety.
Multiple blade type: This model operates mainly using an electric actuator. Based on the application —i.e. Fire, Smoke or Combination Fire & Smoke; the actuator can be configured with the Building management system (BMS) or a smoke detector. The electric actuator is energized with power supply to keep the damper open under normal conditions. When heat/smoke is detected by the thermal responsive device (TRD) / smoke detector, power supply to actuator will be disconnected.
Should the BMS be used to close the actuator, it has to be configured to disconnect power supply to actuator. Once the circuit is open, the damper closes automatically by the force of the springs inside the actuator. Such actuators are otherwise known as spring return actuators. TRD’s are supplied with a reset button to re-establish power supply thereby keeping the damper in open position.
The open/close position can be monitored by introducing a limit switch or Auxiliary switch in the damper which communicates the open/close status to the BMS or a standalone control panel. As a result, further actions could be programmed like switching on smoke extract fans or switching off all HVAC units or informing Fire department and so on.
Airmaster has taken great efforts in developing fire dampers and getting it certified from UL after passing their stringent testing procedures successfully. Our dampers have withstood the demanding test requirements of UL 555 and UL 555S standards. Both these standards call of series of tests like: cycling test for operational reliability, salt water spray test, fire endurance test followed by high pressure hose stream test, leakage test, dynamic closure test and overall integrity of the damper is also checked. Quality inspection is carried out on regular basis by UL representatives to ensure if manufacturing is done be per the mandate.
UL listed products are finally dispatched after UL labels are proudly pasted on each and every fire damper. The installation has to be carried out strictly as per the installation instructions that is sent along with every shipment.
Hose Steam Test
Most common installation errors to be avoided:
- Fixing of duct directly to the Fire damper frame is not allowed.
- Rigid Duct — Sleeve connection without complying sleeve thickness recommended by SMACNA (table 5-2). It is important to note that improper installation procedures could render UL listing of the damper null and void.
The Time / Temperature curve achieved during the fire test by UL laboratory is as shown above .
Handling & Storage: Fire dampers are sensitive products made for the sole purpose of saving life and property. Therefore extreme care must be taken while handling fire dampers during loading, off-loading and storage at site against any physical damage. All fire dampers must be stored in a safe place and must be handled carefully. Dampers especially with actuators and electrical accessories must be stored in a dry enclosed area to avoid condensation. Actuators or damper blades should not be used for lifting during installation
Maintenance: Regular inspection and maintenance of fire damper is essential. NFPA 80 — standard for fire doors and other opening protective states that fire dampers shall require inspection and testing one year after installation. Follow up testing and inspection shall be done every 4 years except in hospitals where the frequency shall be 6 years.