When the type and quantity of chemicals or compressed gases that are present in a laboratory room could pose a significant toxic or fire hazard, the room shall be equipped with provision(s) to initiate emergency notification and initiate the operation of the ventilation system in a mode consistent with accepted safety practices.
A means such as a clearly marked wall switch, pull station, or other readily accessible device shall be installed to enable the room occupants to initiate appropriate emergency notification and simultaneously activate the ventilation system’s chemical emergency (chemical spill, eyewash or emergency shower activation, flammable gas release, etc.) mode of operation if one exists.
- For rooms served by VAV ventilation systems, the Chemical Emergency mode of operation should maximize the room ventilation rate and, if appropriate, increase negative room pressurization. For rooms served by constant air volume (CAV) ventilation systems that utilize a reduced ventilation level for energy savings, the Chemical Emergency mode of operation should ensure that the room ventilation and negative pressurization are at the maximum rate.
- Operation of the room ventilation system in a chemical emergency mode should not reduce the room ventilation rate, room negative pressurization level, or hood exhaust airflow rate.
A means such as a wall-mounted “FIRE ALARM” pull station or equivalent shall be installed to enable the room occupants to initiate a fire alarm signal and simultaneously activate an appropriate fire emergency mode of operation for the room and/or building ventilation system.
For rooms served by VAV ventilation systems, the fire emergency mode of operation should maximize the exhaust airflow rate from the hoods and other room exhaust provisions, and also reduce the room supply makeup air. For rooms served by CAV ventilation systems that utilize a reduced ventilation level for energy savings, the fire emergency mode of operation should ensure that the maximum exhaust airflow rate from the hoods and other room exhaust provisions are in effect, and should also reduce the room supply makeup air.
Note, however, that ventilation supply/exhaust imbalance can make the doors extremely difficult to open. Consider programming in a short delay into the fire alarm system (30–60 sec or more) between activation of building evacuation alarms, and shifting the ventilation system to the fire-emergency mode of operation. This delay will allow occupants to evacuate prior to making the doors difficult to operate. The sequence of operations of the emergency ventilation response must take into account the possible conflicting needs of smoke containment and emergency egress. The Fire Authority Having Jurisdiction and the local EH&S office must concur on the configuration of the fire emergency mode of operation.