Measures being suggested to protect buildings against terrorist attacks could instead create immediate problems for building occupants, according to the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE).

As building owners and operators look for ways to safeguard occupants, some are closing air intakes to prevent the introduction of hazardous materials into ventilating systems. But according to professionals skilled in indoor environmental control, these well-intentioned actions could create extensive health problems.