Fire Safety - Ventilation System
1. Comfort HVAC Systems:
– Purpose: Designed to maintain comfortable indoor temperatures, humidity levels, and air quality for occupants’ comfort.
– Components: Includes heating, ventilation, and air conditioning units that regulate temperature and airflow.
– Operation: Operates based on user settings and preferences, often with adjustable thermostats and controls.
– Pressure: Generally operates at normal atmospheric pressure levels and is not required to handle high-pressure conditions.
2. Fire Safety Ventilation Systems:
– Purpose: Intended to control smoke and heat during a fire to ensure safe evacuation and protect building structures.
– Components: Includes smoke extraction fans, fire dampers, and pressurization systems to manage smoke and maintain safe escape routes.
– Operation: Functions automatically in response to fire detection systems, often operating under high-pressure conditions and designed to remain operational during a fire.
– Pressure: Must withstand high temperatures and pressures typical of fire scenarios and comply with stringent safety codes and standards.
In summary, comfort HVAC systems focus on providing a pleasant indoor environment, while fire safety ventilation systems are specifically engineered to manage smoke and heat during emergencies, ensuring safety and compliance with fire safety regulations.
HVAC Fire Dampers
3.4.8.1 Air conditioning and mechanical ventilation requirements of different rooms or areas in any occupancy shall be as given in Part 8 ‘Building Services, Section 1 Lighting and Natural Ventilation’ and ‘Section 3 Air conditioning, Heating and Mechanical Ventilation’ of the Code.
Air conditioning and ventilating systems shall be so installed and maintained as to minimise the danger of spread of fire, smoke or fumes from one floor to other or from outside to any occupied building or structure.
Many high-rise buildings integrate smoke management systems into their conventional HVAC systems. In such installation, it requires special design considerations,including safe and adequate controls, acceptable and documented testing and regular maintenance systems.
Wherever batteries are provided the same shall be segregated by 120 min fire rated construction. Ventilation to the room shall be provided as per manufacturer’s instructions.
3.4.8.2.1 From fire safety point of view, separate air handling units (AHU) for each floor shall be provided so as to avoid the hazards arising from spread of fire and smoke through the air conditioning ducts. The air ducts shall be separate from each AHU to its floor and in no way shall interconnect with the duct of any other floor. Within a floor it would be desirable to have separate air handling unit provided for each compartment.
Air handling unit shall be provided with effective means for preventing circulation of smoke through the system in the case of a fire in air filters or from other sources drawn into the system, and shall have smoke sensitive devices for actuation in accordance with the accepted standard [4(8)] and control.
3.4.8.2.2 Shafts or ducts, if penetrating multiple floors, shall be of masonry construction with fire damper in connecting ductwork or shall have fire rated ductwork with fire dampers at floor crossing. Alternatively, the duct and equipment may be installed in room having walls, doors and fire damper in duct exiting/entering the room of 120 min fire resistance rating. Such shafts and ducts shall have all passive fire control meeting 120 min fire resistance rating requirement to meet the objective of isolation of the floor from spread of fire to upper and lower floors through shaft/duct work.
NOTE-Zoned and compartmented HVAC systems are encouraged with an approach to avoid common exhaust shafts and fresh air intake shafts which will limit the requirement of such passive measure and fire rated duct work and dampers.
3.4.8.2.3 The air filters of the air handling units shall be made of non-combustible materials.
3.4.8.3.1 Air ducts serving main floor areas, corridors, etc, shall not pass through the exits/exit passageway/ exit enclosure. Exits and lift lobbies, etc, shall not be used as return air passage.
3.4.8.3.2 As far as possible, metallic ducts shall be used even for the return air instead of space above the false ceiling.
3.4.8.3.3 Wherever the ducts pass through fire walls or floors, the opening around the ducts shall be sealed with materials having fire resistance rating of the compartment. Such duct shall also be provided with fire dampers at all fire walls and floors unless such ducts are required to perform for fire safety operation; and in such case fire damper may be avoided at fire wall and floor while integrity of the duct shall be maintained with 120 min fire resistance rating to allow the emergency operations for fire safety requirements.
3.4.8.3.4 The ducting within compartment would require minimum fire resistance rating of 30 min. Such ducting material in substantial gauge shall be in accordance with good practice [4(9)]. If such duct crosses adjacent compartment/floor and not having fire dampers in such compartment/floor, it would require fire resistance duct work rating of 120 min. The requirements of support of the duct shall meet its functional time requirement as above.
3.4.8.3.5 The materials used for insulating the duct system (inside or outside) shall be of non-combustible type. Any such insulating material shall not be wrapped or secured by any material of combustible nature.
3.4.8.3.6 Inspection panels shall be provided in the ductwork to facilitate the cleaning accumulated dust in ducts and to obtain access for maintenance of fire dampers.
3.4.8.4.1 These dampers shall be evaluated to be located in supply air ducts, fresh air and return air ducts/ passages at the following points:
- At the fire separation wall,
B)Where ducts/passages enter the vertical shaft,
- c) Where the ducts pass through floors, and
- d) At the inlet of supply air duct and the return air duct of each compartment on every floor.
3.4.8.4.2 Damper shall be of motorized type/fusible link. Damper shall be so installed to provide complete integrity of the compartment with all passive fire protection sealing. Damper should be accessible to maintain, test and also replace, if so required. Damper shall be integrated with Fire Alarm Panel and shall be sequenced to operate as per requirement and have interlocking arrangement for fire safety of the building. Manual operation facilities for damper operation shall also be provided.
a) In building design, compartmentation plays a vital part in limiting the spread of fire and smoke. The design should ensure avoidance of spread of smoke to adjacent spaces through the various leakage openings in the compartment enclosure, such as cracks, openings around pipes ducts, airflow grills and doors. In the absence of proper sealing of all these openings, smoke and toxic gases will obstruct the free movement of occupants of the building through the exits. Pressurization of staircases is of great importance for the exclusion of smoke and toxic gases from the protected exit.
b) Pressurization is a method adopted for protecting the exits from ingress of smoke, especially in high-rise buildings. In pressurization, air is injected into the staircases, lobbies, etc, as applicable, to raise their pressure slightly above the pressure in adjacent parts of the building. As a result, ingress of smoke or toxic gases into the exits will be prevented. The pressurization of staircases and lift lobbies shall be adopted as given in Table 6.
The pressure difference for staircases shall be 50 Pa.
Pressure differences for lobbies (or corridors) shall be between 25 Pa and 30 Pa. Further, the pressure differential for enclosed staircase adjacent to such lobby (or corridors) shall be 50 Pa. For enclosed staircases adjacent to non-pressurized lobby (or corridors), the pressure differential shall be 50 Pa.
c) Equipment and ductwork for staircase pressurization shall be in accordance with one of the following:
1) Directly connected to the stairway by ductwork enclosed in non-combustible construction.
2) If ducts used to pressurize the system are passed through shafts and grills are provided at each level, it shall be ensured that hot gases and smoke from the building cannot ingress into the staircases under any circumstances.
d) The normal air conditioning system and the pressurization system shall be designed and interfaced to meet the requirements of emergency services. When the emergency pressurization is brought into action, the following changes in the normal air conditioning system shall be effected:
1) Any re-circulation of air shall be stopped and all exhaust air vented to atmosphere.
2) Any air supply to the spaces/areas other than exits shall be stopped.
3) The exhaust system may be continued provided,
i) the positions of the extraction grills permit a general air flow away from the means of egress;
ii) the construction of the ductwork and fans is such that, it will not be rendered inoperable by hot gasses and smoke; and
iii) there is no danger of spread of smoke to other floors by the path of the extraction system which can be ensured by keeping the extraction fans running.
e) For pressurized stair enclosure systems, the activation of the systems shall be initiated by signaling from fire alarm panel.
f) Pressurization system shall be integrated and supervised with the automatic/manual fire alarm system for actuation.
g) Wherever pressurized staircase is to be connected to unpressurized area, the two areas shall be segregated by 120 min fire resistant wall.
h) Fresh air intake for pressurization shall be away (at least 4 m) from any of the exhaust outlets/grille.
4.6.1 Smoke Exhaust and Pressurization of Areas Above Ground
Corridors in exit access (exit access corridor) are created for meeting the requirement of use, privacy and layout in various occupancies. These are most often noted in hospitality, health care occupancies and sleeping accommodations.
Such as Exit access corridors of guest rooms and indoor patient accommodations department/areas having patients lacking self preservation and for sleeping apartments, custodial, penal and mental institutions, etc, shall be provided with 60 min fire resistant wall and 20 min self-closing fire doors along with sealing of penetrations. all fire stop.
Smoke exhaust system having make-up air and exhaust air system or alternatively pressurization system with supply air system for these exit access corridors shall be required.
Smoke exhaust system having make-up air and exhaust air system shall also be required for theatres/auditoria.
Such smoke exhaust system shall also be required for large lobbies and which have exit through staircase leading to exit discharge. This would enable eased exit of people through smoke controlled area to exit discharge.
All exit passageway (from exit to exit discharge) shall be pressurized or naturally ventilated. The mechanical pressurization system shall be automatic in action with manual controls in addition. All such exit passageway shall be maintained with integrity for safe means of egress and evacuation. Doors provided in such exit passageway shall be fire rated doors of 120 min rating.
Smoke exhaust system where provided, for above areas and occupancies shall have a minimum of 12 air changes per hour smoke exhaust mechanism. Pressurization system where provided shall have a minimum pressure differential of 25-30 Pa in relationship to other areas.
The smoke exhaust fans in the mechanical ventilation system shall be fire rated, that is, 250°C for 120 min.
For naturally cross-ventilated corridors or corridors with operable windows, such smoke exhaust system or pressurization system will not be required.
4.6.2 Smoke Exhaust and Pressurization of Areas Below Ground
Each basement shall be separately ventilated. Vents with Cross-sectional area (aggregate) not less than 2.5 percent of the floor area spread evenly round the perimeter of the basement shall be provided in the form of grills, or breakable stall board lights or pavement lights or by way of shafts.
Alternatively, a system of mechanical ventilation system may be provided with following requirements:
a) Mechanical ventilation system shall be designed to permit 12 air changes per hour in case of fire or distress call. However, for
normal operation, air changes schedule shall be as given in Part 8 ‘Building Services, Section 3 Air conditioning, Heating and Mechanical Ventilation’ of the Code.
b) In multi-level basements, independent air intake and smoke exhaust shafts (masonry or reinforced concrete) for respective basement levels and compartments therein shall be planned with its make-up air and exhaust air fans located on the respective level and in the respective compartment. Alternatively, in multi-level basements, common intake masonry (or reinforced cement concrete) shaft may serve respective compartments aligned at all basement levels. Similarly, common smoke exhaust/outlet masonry (or reinforced cement concrete) shafts may also be planned to serve such compartments at all basement levels. All supply air and exhaust air fans on respective levels shall be installed in fire resisting room of 120 min. Exhaust fans at the respective levels shall be provided with back draft damper connection to the common smoke exhaust shaft ensuring complete isolation and compartmentation of floor isolation to eliminate spread of fire and smoke to the other compartments/floors.
c) Due consideration shall be taken for ensuring proper drainage of such shafts to avoid insanitation condition. Inlets and extracts may be terminated at ground level with stall board or pavement lights as before. Stall board and pavement lights should be in positions easily accessible to the fire brigade and clearly marked ‘AIR INLET’ or ‘SMOKE OUTLET’ with an indication of area served at or near the opening.
d) Smoke from any fire in the basement shall not obstruct any exit serving the ground and upper floors of the building.
e) The smoke exhaust fans in the mechanical ventilation system shall be fire rated, that is, 250°C for 120 min.
f) The smoke ventilation of the basement car parking areas shall be through provision of supply and exhaust air ducts duly installed with its supports and connected to supply air and exhaust fans. Alternatively, a system of impulse fans (jet fans) may be used for meeting the requirement of smoke ventilation complying with the following:
1) Structural aspects of beams and other down stands/services shall be taken care of in the planning and provision of the jet fans.
2) Fans shall be fire rated, that is, 250°C for 120 min.
3) Fans shall be adequately supported to enable operations for the duration as above.
4) Power supply panels for the fans shall be located in fire safe zone to ensure continuity of power supply.
5) Power supply cabling shall meet circuit integrity requirement in accordance with accepted standard [4(13)].
The smoke extraction system shall operate on actuation of flow switch actuation of sprinkler system. In addition, a local and/or remote ‘manual start-stop control/switch’ shall be provided for operations by the fire fighters.
Visual indication of the operation status of the fans shall also be provided with the remote control.
No system relating to smoke ventilation shall be allowed to interface or cross the transformer area, electrical switchboard, electrical rooms or exits.
Smoke exhaust system having make-up air and exhaust air system for areas other than car parking shall be required for common areas and exit access corridor in basements/underground structures and shall be completely separate and independent of car parking areas and other mechanical areas.
Supply air shall not be less than 5 m from any exhaust discharge openings.
5.7 Fire Dampers
5.7.1 A fire-actuated damper shall be installed in the supply air plenum at each point where a supply air duct inlet or a supply air outlet penetrates the continuously welded shell of the assembly.
5.7.2 The fire damper shall be certified for such use or be part of a certified exhaust hood with or without exhaust damper.
5.7.3 The actuation device shall have a maximum temperature rating of 141 °C.
5.7.4 Supply air plenums that discharge air from the face rather than from the bottom or into the exhaust hood and that are isolated from the exhaust hood by the continuously welded shell extending to the lower outermost perimeter of the entire hood assembly shall not require a fire-actuated damper.
Ductless Jet Fan System
Jet fan systems have been developed to ventilate underground car parks, addressing both carbon monoxide (CO) removal during normal conditions and smoke extraction during emergencies. A single system, the jet fan ductless car park ventilation system, handles these needs more effectively and economically.
The system includes jet fans and main axial fans for both air extraction and fresh air supply. Fresh air fans are typically used in basements where natural ventilation openings, such as shafts or ramps, are insufficient. Additionally, a unique control system, tailored to specific projects, adjusts the fans’ speeds based on signals from CO, heat, and smoke sensors, optimizing energy usage.
To design an efficient system, early collaboration with designers is essential to determine the appropriate openings in the basement for effective fresh air intake and CO/smoke removal. Fans are usually designed according to air exchange rates required for both routine and emergency situations. Local codes and building regulations play a crucial role in shaping airflow, control systems, and zoning within the basement.
Jet fans operate based on CO sensor signals, enabling energy savings through a “working on demand” principle. They can be controlled individually or in groups by fire zones. During fire emergencies, the entire system—including fresh air fans, extract fans, and jet fans—runs at full speed to rapidly and efficiently clear smoke from the basement.
Jet fan systems offer several benefits compared to traditional ducted ventilation systems:
Reduced Ceiling Height: Without the need for ducts, jet fan systems allow for a lower ceiling height, typically reducing it by approximately 0.5 to 0.75 meters compared to conventional basements.
Faster Installation: Jet fan systems are quicker and simpler to install than conventional ducted systems, which are often more expensive and complex. This leads to reduced installation time and costs.
Ease of Maintenance: These systems are easy to maintain and are ideal for use in renovated car parks.
Zone-Based Operation: Jet fan systems can operate in specific zones based on signals from CO and smoke sensors, enhancing efficiency and targeting ventilation needs more accurately.
Improved Air Quality: Jet fans facilitate better air mixing by directing air flow, leading to improved air quality in the basement compared to traditional ducted systems.
Integrated CO and Smoke Extraction: Jet fan systems combine CO and smoke extraction into a single, highly automated and efficient system. CO sensors ensure that only the fans in polluted areas operate, while smoke sensors trigger full-system activation when needed.
Lower Resistance and Energy Use: The absence of ducts reduces resistance for the main fans, resulting in lower static pressure and reduced motor power requirements.
Flexible Fan Placement: Jet fans offer flexibility in their placement within the car park, allowing for optimized air distribution.
Cleaner Aesthetic: The low profile of jet fans contributes to a cleaner and neater appearance in the car park, which can be monitored more effectively with CCTV.
Structural Protection: By providing efficient air mixing and quick smoke removal, jet fan systems help prevent costly structural damage during fire emergencies, limiting heat exposure to ceilings and slabs.
The design of a jet fan ventilation system involves several key components and considerations:
Jet Fans:
- Requirement: The number and capacity of jet fans are determined based on the size of the basement to ensure effective air movement and ventilation.
Main Fans:
- Fresh Air Fans: Required when natural ventilation cut-outs are insufficient.
- Extract Fans: Necessary for CO and smoke removal, with capacities based on air change rates. International codes recommend 4-6 Air Changes per Hour (ACH) for CO removal and 8-10 ACH for smoke extraction.
Control System:
- Role: The control system is crucial, as it manages the response time and speed of the jet fans based on signals from CO, heat, and smoke sensors. This optimization helps in managing energy efficiently across different parking loads throughout the day.
- Functionality: It starts and stops fans individually or by zones, depending on the demand in various areas of the car park. When connected to fire detection systems or in the presence of high CO levels, the control system will activate fans at full speed upon receiving signals from sensors.
- Fire Scenario Management: In case of fire, the control system not only boosts the speed of jet fans on the fire floor but also turns off fans on other floors (both above and below the fire floor) to prevent the spread of smoke.
- Regulation: The system also manages the operation of main supply and extract fans based on sensor signals, ensuring quick and effective response.
Overall, careful design and integration of these components ensure that the jet fan system operates efficiently and effectively, meeting both regular ventilation needs and emergency requirements.
International Mechanical Code – Section 403.5:
- Public Garages: Mechanical ventilation systems in public garages are not required to operate continuously. Instead, these systems should be designed to activate automatically upon detecting a carbon monoxide (CO) concentration of 25 ppm using approved detection devices.
Uniform Building Code – Section 705:
- Parking Garages: In all parking garages, automatic CO sensing devices may be used to regulate the ventilation system. The goal is to maintain an average CO concentration of no more than 50 ppm over an eight-hour period, with a peak concentration not exceeding 200 ppm for any one-hour period.
State, Municipal, and Other Building Codes:
- Local Regulations: Most state and local building codes recognize and recommend the use of CO monitors in enclosed parking garages. In the absence of specific CO monitoring provisions in local codes, it is crucial to understand that carbon monoxide remains a hazardous gas to health and safety. Therefore, applying sound judgment and best practices by design engineers is essential in ensuring safety.
First Alarm Level:
Threshold: Set for a low concentration of carbon monoxide (CO). (Refer to the table for recommended low alarm levels.)
System Response: The gas monitoring system should activate exhaust fans and outside air intake devices to reduce the CO level to an acceptable range.
Optional Action: If the parking structure has two-speed fans or a second set of fans, only the first speed or the first set of fans should be activated initially.
Second Alarm Level:
Threshold: Set for a high concentration of CO. (Refer to the table for recommended high alarm levels.)
System Response: Ventilation equipment that was activated at the low alarm level should continue to operate.
Optional Action: If the parking structure includes two-speed fans or a second set of fans, these should be activated at full speed or all available fans should be turned on.
Additional Measures: The activation of a strobe light (red) and horn may be required to alert occupants.
Evacuation: People may need to evacuate the parking garage to ensure safety.