Smoke Evacuation for Ambulatory Surgery Centers
July 1, 2008
Part 1: Requirement and Enforcement
A ventilation system shall be provided in all anesthetizing areas per NFPA 99 that is capable of automatically venting smoke and products of combustion.This requirement is enforced by the Department of Health Service Regulation (DHSR) and the system will be tested during the final walk through by a DHSR representative.Therefore a smoke evacuation system is required for all operating rooms.
However, this requirement is not found in the North Carolina Building Code and therefore it is typically not enforced by the local building inspector.The North Carolina Building code does address smoke control systems which are required in high rises, underground facilities, enclosed parking decks, etc.Anesthetizing areas are not listed in the building code as an area that is required to have a smoke control system and therefore a smoke evacuation system is provided but not a smoke control system.Typically, the local official will not require, enforce or even test the smoke evacuation system.
The building code requirements for a smoke control system are very detailed and determining the exhaust rate alone can be difficult.Since a smoke control is not required in an anesthetizing area, the smoke control system section in the state building code is not required to be adhered to. A smoke control system will require a 1 hour rated fire command room that is not usually planned for in an ambulatory surgery space (ASC).Also, the smoke exhaust rate is usually greater with a smoke control system.
The building code does have a exception to the requirement of fire and smoke dampers in ducts that are a part of the smoke control system that penetrate rated walls.The theory behind the exception is to prevent a smoke or fire damper from closing during an emergency that could hinder the operation of the smoke control system.However, per local code officials in Mecklenburg County, the exception does not apply unless the smoke evacuation system is a required system as outlined in the North Carolina Building Code.As mentioned above, an ASC does not fall into the category of having a required smoke control system per the building code and therefore the exception was not allowed to be utilized.The local code official required smoke dampers at the rated smoke barrier wall even though there was an understanding that the ductwork was part of the smoke evacuation system that was required by NFPA 99.
When DHSR visited the site to perform their final walk-through, the question was asked why the smoke dampers were installed in ducts that were part of a smoke evacuation system.The DHSR representative did not agree with the local code officials requirement of the smoke dampers but agreed to leave the dampers in since the local authority having jurisdiction had required it.
In short, when a smoke evacuation system is to be utilized, the first step is to determine the type of system to be provided and clarify system requirements and fire and smoke damper requirements with the local building official and with DHSR to avoid any conflicts at the end of the project.
Part 2:Design and Performance
The typical method of providing a smoke evacuation system is to utilize the air handling unit that is serving the operating room.Upon a signal from the fire alarm system, the unit goes into an economizer mode and provides 100% outside air and relieves 100% of the air to the outside.The system continues to operate this way until smoke is detected in either the supply duct or the outside air duct which would shut down the supply fan while the return fan continues to operate.DHSR guidelines require any intake to be located a minimum of 30’-0” from any exhaust.Therefore, when the air handling unit is utilized as the smoke evacuation system, the outside air intake on the air handling unit must be ducted 30’-0” from the relief of the air handling unit.A dedicated exhaust fan may also be used in lieu of the air handling system.
All fan motors and controls that are part of the smoke evacuation system must be on emergency power to allow the system to operate upon a loss in power to the building.The controls must also be sequenced that activation of the emergency stop switch does not interfere with the smoke evacuation system of the air handling unit.
The design performance of a smoke evacuation system is largely up to the design engineer.Neither NFPA nor the North Carolina Building provides any guidelines for the performance of a smoke evacuation system. Therefore the amount of smoke used in a smoke test and the length of time required to adequately ventilate the room can be determined by the mechanical engineer.Our typical test requires the mechanical contractor to provide enough smoke bombs to fill the operating room with smoke based on the volume of the room.Once the smoke test has started, the smoke evacuation system or sequence should start within 30 seconds.Then 5 minutes after the start of the test; a person should be able to see an exit from any location within the operating room.
