Page 31 - Occupational Health & Safety, February 2018

deployed in low hazard laboratories. Maintaining a lab operational permit system with periodic checkups is advisable.
An air sampling pump sequentially delivers packets of air from each connected sensing tube to a centralized sensor suite. Depend- ing on the array configuration, delay times up to the maximum allowed 15 minutes are possible. The PID used in the system uses a 10.6 eV bulb. Flammable gases or vapors with a higher ionization potential, for example, hydrogen, are invisible to the system.
A laboratory operations permit system should set threshold limits to the use of oxygen-depleting agents. For example, the haz- ards from spillage, dispensing, or use of liquid nitrogen have to be considered.
Energy Savings Evaluation
The optimization system used at NU reduces the general labora- tory exhaust and respective fresh air inflow, but it does not regulate fume hood exhausts. Laboratories in which the number of fume hoods demands high exhaust ventilation will not realize energy savings. In equipment rooms where the equipment heat loads de- mand high ventilation rates for cooling, there is nothing to gain from the system. However, future laboratory equipment design conversion from air to liquid heat exchange may lead to additional energy saving opportunities in these spaces.
Chemistry teaching labs have a large number of fume hoods
but only limited daily or periodic use. At other times, the fume hoods may be empty. Best design practice may be to manually turn all fume hoods’ exhaust on/off using a master switch. In- vestment in an optimization system may have limited payback in these areas but could provide lab monitoring capabilities.
Because the system’s particulate sensor monitors only two par- ticle size bins, it usually is not used to dynamically control ISO Class 1-6 cleanroom ventilation rates. Currently, NU is investigating the use of the particle sensing technology for ISO Class 7 – 9 clean areas.
The best payback may be achieved in vivarium animal spaces. Animal releases of VOC and particulate into the secondary barrier (the room) will dynamically open ventilation valves for more fresh air. With directly ventilated cage racks this release is not frequent. We expect significant energy savings when the ventilation rate can be kept well below the traditional 15 air change design for vivaria.
Efforts to accurately quantify NU total laboratory energy savings are continuing. In addition, NU uses the data delivered through these ventilation optimization systems to diagnose air quality or temperature-related issues that may arise during labora- tory operation.
Markus Schaufele, MS, CSP, is Manager of Standards, Compliance and Emergency Planning in the Office for Research Safety of North- western University.
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