Demand Control Ventilation: When Is It Most Appropriate?

Laboratory airflow demands

By necessity, the task of the EH&S team at any research university or other large research institution is broad and varied. From training researchers on safe lab practices, responding to incidents, networking with outside groups like fire marshals and facilities departments, to doing safety outreach and now deploying “green lab” outreach initiatives; the task of the EH&S team is to mitigate risk and to keep everyone safe working within the laboratories.

Lab dilution ventilation is just one of the components that goes into protecting occupants, and it should be made clear that there is no ventilation that can rectify truly unsafe lab practices.

Traditionally, the practice was to maximize air change rates (ACH). With ACH of 12+ per hour, the idea was that any potential hazardous chemicals are highly diluted, thus keeping the occupants safe. But there are three problems with this practice. First, following a spill, the higher ACH flowing over a spill actually causes an increased evaporation and subsequent higher exposure. Next, in some cases, these higher ACH rates – which are extremely expensive – are turned down substantially at night, causing unsafe conditions for those initially entering or returning into a lab when unknown events have occurred, and/or when entering during ‘unoccupied hours’. Lastly, this practice also causes enormous energy expense, using more air than needed for the vast majority of the time. 

The idea with a demand-based approach is to solve all of these challenges simultaneously. Ventilation is optimized, providing more air when needed and avoiding over-ventilation when it is not. Just as important is the benefit of insight and intelligence to see what is happening, where and when, across a large footprint.

Demand control ventilation poses a workable solution for EH&S airflow challenges. DCV systems seek to address the deficiencies inherent in fixed-rate ventilation systems by balancing safety with energy efficiency. Air exchange rates can now be tied to real-time data so ventilation can be variable and based on current conditions in the lab, versus arbitrarily static – either wasting energy or providing less air then desired when and where it’s needed. Also, by providing intelligent insight into the operations of the lab, principal investigators (PIs), researchers, and now EH&S professionals can all have a real-time window into lab practices. In the past, this only happened when reacting to an event, at which point it is too late.

Benefits of DCV in action

Demand-based platforms are not to be considered a part of a lab’s threat detection system, as they do not detect and remove airborne agents that are immediately toxic. Dilution ventilation is not a replacement for safe lab practices! However, continuous data collection and reporting identifies the protection provided in the form of increased ventilation during events and opportunities to improve safe lab practices through interpretation of events and behaviors.

With DCV, EH&S personnel can measure how many events are occurring, where and when they happen, as well as frequency, duration, and indications of cause. This data can then be accessed by PIs and other researchers as well as the EH&S team, in order to identify training and maintenance needs. Given this, intelligent demand-based control is protecting occupants through air change rate variation while also saving substantial energy. Additionally, in rare instances when a fume hood may malfunction or a lab occupant may accidentally create a fugitive emission from a fume hood, the monitoring capability can capture this data. The system automatically increases air change rates and logs the event as part of the data reporting.

Real life examples

A university EH&S professional had just logged into a DCV dashboard when an incident jumped out at him – more than 2000 parts per million (ppm) of carbon dioxide (CO2) had been detected in a room for about 24 hours. He immediately went to the room and investigated the cause. After a bit of exploration, he discovered a faulty CO2 gas piping connection on a piece of equipment. The piping was then fixed and the leak went away. By using the analytics to identify the leak as CO2, however, the university had been able to save money associated with performing additional leak testing on all of its gas piping systems. In addition, the data showed that the DCV system responded with increased ventilation rates as designed.

In another example, at a laboratory in a leading research university in Philadelphia, the DCV system flagged a particular day of the week and time of day when contamination levels outside of the normal range were regularly occurring. The university’s EH&S personnel were able to use that data to identify a particular lab technician who was employing unsafe practices, re-train that technician, and greatly reduce the overall risk of exposure to the contaminants over time.

Deploying demand-based control intelligently. The U.S. Department of Energy has adopted, and is now promoting, a Smart Lab concept pioneered by University of California-Irvine. The agency has published a decision tree to properly and intelligently deploy demand-based control across over 1,500 lab spaces on the campus. This decision tree found that approximately 86 percent of all spaces qualified for demand-based control. This means that certain spaces may require much higher base level ACH rates – it is an owner’s decision to determine whether monitoring of IEQ should be done instead of demand-based control. In short, it remains critical to understand where hazardous materials exist and to train and promote safe lab practices when working under hoods with hazardous chemicals.

Technology enhances monitoring capabilities. Intelligent, demand-based control technology provides EH&S personnel with the ability to have a set of “eyes” in each lab at all times. This helps them to determine whether existing safety practices are working, provides data for re-training when necessary, and preserves occupant safety by optimizing lab dilution air, as needed. In doing so, the platform enables EH&S teams to take a proactive approach to laboratory airflow safety. They can use the data to reduce the burden of daily tasks and allow EH&S staff to focus on higher value organizational change.

At the same time, this smart platform significantly decreases energy usage through the elimination of over-ventilation. Incorporating an intelligent system into a research center’s air management is not about reducing air, but instead about maintaining the health and safety of all laboratory occupants and adding a layer of insight that was previously not available. Remember, not all labs are suited for DCV technology and it should be intelligently deployed with careful coordination between the facilities team, EH&S and experienced third-party professionals when needed.

When deployed appropriately, however, the technology offers the dual benefit of substantial savings and new insight and intelligence for their EH&S and PI staffs. This reduces risk, generates savings, and leverages advances that have been made with these new approaches. Certainly the successes with many leading research institutions should be testament to others considering adopting and deploying demand-based control – less money, more air when needed, and insightful data amount to considerable advantages.

For more information on DCV technology, click here.