Two universities and two firms in Washington state are developing equipment that uses photoacoustics to monitor air for potentially deadly biological agents in environments ranging from mailrooms to airports.Eastern Washington University in Cheney is collaborating with InnovaTek in Richland, Quantum Northwest in Spokane and Washington State University in Pullman to develop the equipment, which uses laser pulses to excite light-absorbing substances that release energy as heat. The heat-induced solvent expansion results in a release of energy in the form of sound waves. The device measures the unique signature of the waves with an ultrasonic transducer and determines what particles emitted them.Testing was slated to begin in January. The researchers hope that further improvements will make the equipment small and quiet enough for use in homes someday.