TECHNICAL FEATURE CO2 sensing is commonplace but there are other indoor contaminants that should be considered. These contaminants commonly include VOC (primarily benzene, toluene and xylene that is often the result of outgassing from indoor finishes and fabrics) and particles of various sizes. Sensor technology continues to evolve, expanding the type of contaminates sensed. One manufacturer has developed a sensor that will combine VOC and CO2 with an output very similar to CO2.7 This performance is illustrated in Figure 2. Some designs assume that indoor air quality is different than outdoor air quality. But Standard 62.1 suggests that 15 cfm (7 L/s) of outdoor air per person is sufficient to satisfy occupant need for good IAQ. In the author's opinion, Standard 62.1 can be used in any occupied space (including labs) to satisfy occupant's needs for good IAQ. In addition to occupant needs, there are the needs for containment devices including fume hoods, biosafety cabinets, snorkels and other ventilation. The author suggests that the EPA's six contaminants be used for monitoring indoor air. Several contaminants can be filtered in the supply air-handling unit (AHU) so not all contaminants need to be measured in the space. A velocity sensor can be located at the entry to the fume hood continuously, ensuring that the occupants are in "fresh" air. A theoretical alternate for indoor measurement is to continuously measure any contaminates that might possibly escape from the hood, but this is a complex task and just not practical. Often, a chemical treatment kit is used for spills rather than extra ventilation. The extra ventilation can cause the spill to vaporize more quickly than normal ventilation.8 Owner Considerations Operational considerations include specifying the laboratory use and control of chemicals. Often special hoods are used (perchloric acid) when specific laboratory requirements dictate. Sorting the grade of the chemicals (banding) is often used to identify unique chemicals for use in dedicated hoods. The client www.info.hotims.com/54424-138 JAN UARY 2015 ashrae.org ASHRAE JOURNAL 17