Specifies that filters with a MERV rating of not less than 6 be installed upstream of all cooling coils. Specifies that gas phase adsorbers (typically activated carbon) be used to control gaseous contaminants when needed to provide an adequate level of indoor air quality. An ASHRAE Group was appointed to provide guidance on actions that should be taken to reduce the health and safety risks of occupants in buildings that might be subjected to extraordinary incidents, whether caused by war, terrorism, accident or natural disaster. The guidelines suggest that buildings incorporate particulate air filters with the highest MERV rating that is physically feasible and economically justified. Consideration of air cleaning should also include the need for gas and vapor removal technology to reduce the building vulnerability to chemical agents.