HVAC Solutions for Reducing Airborne Pathogens

Reducing Airborne Pathogens

Most North Americans spend approximately 90% of their time indoors, whether they are at school, at work, or out shopping. Indoor air quality (IAQ) can have a significant effect on the health of the population.

The quality of the air delivered by an HVAC system is commonly measured by its ventilation effectiveness, which is the ability of the system to remove internally generated airborne pollutants from a space. Generally, the HVAC system removes pollutants through the introduction of fresh, clean air and removal of polluted air. In order to improve the IAQ of an indoor space, the number of pollutants must be reduced. This can be done through:

1. Removing contaminants with filtration to reduce the overall concentration of contaminants.
2. Diluting the number of contaminants in the space by increasing air change rates, specifically with filtered or fresh outdoor air.
3. Increasing ventilation effectiveness, through well designed air movement.

We outline below several solutions that use any or all of the above methods to best suit your application, fit in your budget, and provide improved indoor air quality for your occupants.

Overhead Mixing System with Integrated Filtration

Easy to implement, this solution replaces or modifies existing diffusers to provide MERV 13 or 15 filtration and remove viral particles with at least 95% effectiveness. Implementing filtration at each diffuser effectively reduces the concentration of airborne contaminants, thereby reducing the probability of exposure to airborne germs and viruses. Upgrading a typical overhead mixing system to include filters at each diffuser requires very few changes to the overall HVAC system, keeping the cost of implementation low.These solutions can be used in almost any space including offices, classrooms, and retail are ideal for retrofit applications and suitable for new construction projects as well.

Option 1 - Retrofit Existing Diffusers

Retrofit filtration attachments include a 2", MERV 13 or 15 filter and a secondary diffuser face and are suspended directly below existing diffusers so that ductwork changes are not required. Held in place between the t-bar ceiling grid and the original diffuser, this attachment forces air from the original diffuser through a filter before being discharged through the secondary diffuser face. These retrofit filtration attachments protrude 6" from the ceiling providing a visual reminder of the additional precautions taken to provide air cleanliness. Filters are accessible from the room side, by sliding the filter in or out of the side access panel. The secondary diffuser face is available in any of the 24"x 24" Price t-bar ceiling diffuser styles.Option 2 - New Diffusers with Integrated Ceiling-Access Filters

Diffusers with ceiling-access filters have a 6" plenum box and are installed on top of the t-bar ceiling grid, replacing existing diffusers. These diffusers have integrated MERV 13 or 15 filters that require access to the ceiling plenum for periodic replacement. Filters are slid in or out of this diffuser though a hinged access door on the side of the unit. This diffuser style is available in any of the Price t-bar diffuser models. 

Option 3 - Diffusers with Integrated Room-Side Accessible Filter

Diffusers with room-side accessible filters have a 6" plenum box and are installed on top of the t-bar ceiling grid, replacing existing diffusers. As the name implies, room-side replaceable filters provide convenient access to the filter from the room side for periodic filter replacement. These filters make use of a gel seal on the filter frame and a knife edge flange on the diffuser to create a reliable seal that prevents filter bypass. Filters are available in MERV 13 or 15 for at lest 95% viral particle removal or HEPA for 99.99% filter efficiency. Price offers a number of suitable diffusers including the Louvered Face Diffuser with Filter (AMDC) and Radial Vane Diffuser with Filter (RVDC).

Displacement Supply, Filtered Return, and Room Filtration

These pragmatic solutions use existing ductwork or require minimal retrofitting of ductwork within the zone. Displacement ventilation provides low velocity air at higher temperatures to create a comfortable environment. This type of approach to air delivery relies on natural convection to move the air throughout the space making it energy efficient. The air is supplied at low level and pushes contaminants and particles upwards out of the breathing zone resulting in improved air quality ^2,3,4,5,6 instead of recycling contaminants back into the space. Enhanced filtration of the return air is provided by the MERV 13 filters on the series fan powered terminal unit.These solutions are suitable for new construction and retrofit projects, and can be used in almost any space, including offices, classrooms, and retail.

Option 1 - Ceiling Displacement

A ceiling model DFC displacement diffuser can be installed into an existing ceiling grid removing the existing supply grille. Existing overhead ductwork and terminal units can be used, minimizing overall renovation costs.

• Fits into standard T-bar ceiling grid
• 2’ x 2’ and 2’ x 4’ sizes available
• Low pressure drop minimizes impact on system
• Quiet air delivery
• Comfortable, occupant driven airflow

Option 2 - Ceiling Displacement with Fan Mixing Box