When there is a shortage of air in the lab, it is less costly to provide an auxiliary air fume hood system than to change or enlarge the whole building air handling system. With the sash in the ½-open position, it only requires 50-percent supply air to make up for the exhaust air, making it 100-percent efficient with no room air required.

HEMCO Corporation, www.HEMCOcorp.com, (800) 779-4362.