One of the greatest expenses and energy drains in a cleanroom is the HVAC system. Air change rates, pressurization, temperature, and humidity are all monitored to maintain compliance for cleanroom classification. This accounts for about 80% of the energy used, and about 50% of that comes from that fans alone.
With strict guidelines on air quality and regulation, the HVAC systems are typically left to run at full power all the time. If you can reduce the amount of energy used by the HVAC or even shut the system down while the room is not in use (e.g. evenings and weekends), it would result in a significant cost and energy savings. The question is: is it possible to reduce the air change rates without compromising the microbial growth in a sterile environment?
According to research, yes, it might be possible to cut HVAC usage during periods of inactivity without compromising classification of the room.
Several experiments have been conducted to test this, yielding similar results. However, it is important to note that for your specific cleanroom, you should take this as part of your overall data collection to determine whether your own cleanroom qualifies for turndown or shutoff.
Pharmout.net published some interesting findings in the article “What’s your cleanroom costing you?” by Megan Rutherford. You can read the full details here. To summarize, the experiment took place in an empty Grade C cleanroom that was serviced by an airlock, both with terminal HEPA filtration.
As stated in the article, “A single air handling unit supplied the cleanroom and airlock, providing the cleanroom with up to 45 air changes per hour (AC/H). The system was balanced to provide 15 Pascals positive pressure to the airlock and 30 Pascals positive pressure to the cleanroom, relative to atmospheric pressure.”
What the study concluded was that while there was an increase in non-viable particles during low air change rates, the increase was not significant enough to change classification.
When the air change rate was stopped completely, this experiment found that classification was lost in about twenty minutes. However, depending on the cleanroom, some say you may be able to shut your system down completely on the weekends.
The potential to cut energy usage and accompanying costs by limiting your HVAC system is a game-changer for a lot of companies. The end result is definitely worth your time and resources to find out if this is a possibility for your facility.
For questions or services regarding cleanroom certification or validation, contact Gerbig Engineering Company. We’ve been in this industry for thirty years. 888-628-0056; firstname.lastname@example.org.