As time goes on we find more and more reasons to focus on improving indoor air quality (IAQ). Whether is allergens, pollutants, smells, or even the unknown potential for infection spread, the general public is expecting the air they breathe in the buildings in which they live, work, and play to be filtered or treated. For years, facility owners and operators have had a multitude of options for their buildings’ HVAC systems, but an area that has often been left untreated are the small, enclosed, unconditioned elevators. Hearing from our clients that this was an area of concern, Henderson Building Solutions set out to identify a solution. The result – an elevator cab cleaning system which reverses the standard airflow and introduces an air purifying system that can be applied to any elevator, regardless of manufacturer or conveyance type.
Standard Elevator Airflow
Standard elevators are equipped with a basic exhaust fan that helps circulate air in the elevator cab. The fan is mounted on the top of the car and exhausts air from the cab into the hoistway. The supply of air into the cab is pulled in through the toe kick as a result of the negative pressure caused by this exhaust and the air that is exchanged when the doors open to the building.
New Elevator Airflow
The idea emerged to modify a portable air purification system, which includes MERV 14 filtration with pre- and post-filtration ionization, to replace the exhaust on top of an elevator car. This patent-pending application reverses the air flow within the cab, positively pressurizing the space with filtered air, forcing contaminants out into the hoistway through the toe kick.
How It Works
Operating on three possible speeds – low for small cars, medium for larger cars, and high for cab clearing – the elevator cab cleaning system is controlled by an occupancy sensor. When a rider is using the elevator, the fan operates on low or medium speed. However, when the cab is empty, the unit switches to high speed to flush the space with filtered air and force any lingering contaminants out of the cab and into the hoistway through the toe kick.
We installed one of these units on an elevator in Henderson’s headquarters in July 2020. A team of our commissioning experts executed preliminary tests to demonstrate the system’s efficacy in improving the air quality within the elevator cab by measuring the number of particulates, measured in parts per million (ppm), in the air ranging from .3 – 10 microns (μ) in size and comparing hundreds of air samples taken before and after installation. The results trended positively for the three particulate sizes we focused on. For the smallest particulate size tested, 0.3 μ, the number of impurities showed an increase over time with just a standard exhaust fan, indicating the standard fan was not removing particulates of this size and they were accumulating in the cab air. However, with the new filtration system, the cab contained roughly 75% fewer particulates at the end of the testing than it did after the same period of time with the standard exhaust fan. And for the largest particulate size tested, 10 μ, the system immediately reduced the number of impurities to zero in our testing.
Installing this elevator cab cleaning system is a simple retrofit that can be accomplished in a matter of hours. As a one-to-one replacement of the existing exhaust fan, the unit requires no additional power draw and has no impact on ridership, as it weighs only 12-13 pounds more than a standard exhaust fan. Additionally, the controls are self-contained and do not need to be integrated into a machine room, meaning this system can be added without an elevator modernization – though it could also be easily incorporated into a planned or ongoing modernization. The only modification to the interior of the cab would be the addition of a small LED light that indicates to riders that the cab is protected by a filtration system.
Improving indoor air quality is part of a dynamic approach building owners and operators are taking in making their facilities feel safer for the public. To learn more about this elevator cab cleaning system, contact us today.