The Basics of Air Filtration in HVAC Design

Learn the differences in air filtration and indoor air quality performance within HVAC system designs.

Does your building have an HVAC system? Most likely, it does. But does that mean your building and its occupants have good or even acceptable indoor air quality? There is a good possibility it does not. But why does this matter?

In this article, we’ll look at the differences in air filtration capabilities in HVAC systems, why this can significantly impact indoor air quality, and how these differences affect buildings, their owners, and occupants on several levels. 

What Is An HVAC System?

Almost every public building has a basic air filtration system called HVAC (Heating, Ventilation, and Air Conditioning). These air handling systems are designed to serve a fairly broad purpose: to provide acceptable indoor air quality derived from sufficient ventilation that includes (to varying extents) air filtration and maintaining comfortable indoor air temperature. 

But not all HVAC systems are the same. The air filtration component of HVAC systems is hugely varied. The different styles of filtration, types, and ratings of filters used in HVAC systems are crucial to how effective they are in cleaning the air throughout the HVAC system and, in turn, their impact on a building and its occupants.

Roof Top Commercial HVAC System

How Air Filtration Is Integrated Within HVAC Systems

Originally air filtration systems in an HVAC system were put in place to keep dust accumulation off heating and cooling coils. They have since evolved to fit the changing needs of schools, workplaces, and other building occupants. 

While most HVAC systems still have basic levels of air filtration, which can catch air born particulate and contaminants. Manufacturers have made changes, and improvements to existing designs, and new technologies have enabled the development of systems that can reduce or remove airborne contaminants. 

Air Filtering Through MERV Filters In HVAC System Air Handler Unit

What Airborne Contaminants Do HVAC Systems Remove?

There are lots of contaminants and particulate that can be found within buildings. Contaminants found in building HVAC systems can be grouped into three general categories: 

  1. Particulate (dust, dirt, smoke, etc.) The most common form of airborne matter. 
  2. Gaseous (ozone, nitrogen oxide, nitrogen dioxide, carbon monoxide, and sulfur dioxide). Most of these are introduced from the HVAC system’s fresh air intake, but some can come from off-gassing from synthetic materials inside the building. 
  3. Biological (bacteria, viruses, and fungal organisms). These are the smallest particle contaminants and can come from within the building or be drawn from outside. 

Each type of particle varies in size, and their size is measured in micrometers (microns). For example, gaseous contaminants are usually less than 0.01 microns in diameter, whereas dirt is several thousand microns. Proper air filtration with an HVAC system is needed to reduce the concentration of contaminants inside buildings effectively. 

ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) developed a standard for testing filters to create an unbiased categorization method based on how efficiently an air filtration system removes or reduces various particulates. All filters tested using this standard are rated from 1 to 20. The higher the MERV rating, the better the level of filtration. 

A higher MERV rating doesn’t necessarily mean it’s better for your building. While the highest ratings may mean better filtration efficiency, it causes a greater resistance to airflow within the system - which must be mitigated by rebalancing your system and increasing fan energy use. This can increase your overall energy bill substantially. That’s why building managers need to understand what kind of filter is best for their building and the options. 

Dirty MERV Filter Being Replaced In HVAC System

Why Does Air Filtration In HVAC Systems Matter?

The quality of air inside a building can significantly impact its occupants, and all public buildings and their occupants benefit hugely from effective air filtration. 

From the circulation of common winter viruses that can quickly spread illnesses in schools and offices to allowing bacteria, dust, mold, VOC, and other contaminants to spread, poor air quality can be one of the most significant workplace hazards. 

Environments that do not address air quality can encourage or trigger health problems like allergies and asthma. Poor indoor air quality can increase the likelihood of occupants getting sick, contributing to sick days and increased absenteeism. Studies have proven that poor indoor air quality can lead to cognitive impairment, including poor decision-making, slower reaction times, and other factors linked to productivity. There is also evidence that poor indoor air quality has a detrimental effect on mental health. 

Building owners may find it more challenging to find tenants for their buildings if they don’t offer what is more and more commonly viewed as a basic necessity - good indoor air quality. As well as contributing to the longevity and integrity of the building itself (making air filtration investment a sensible long-term financial choice), excellent air filtration makes the facility more desirable to tenants because it protects their health and has a positive impact on their own business.  

Facility Manager Planning Sustainable Building Upgrades

How To Chose The Best Air Filtration System For Your Building

Multiple factors will impact the decision on which air filtration system is suitable for your HVAC system—considering every aspect of the building, its construction, interior volume, and how it’s used, and determining if you need a flexible or permanent solution. Efficiency measures are also a consideration, such as air exchanges per hour (ACH) and cubic feet per minute (CFM). 

For unbiased advice and support to find the best air filtration solution for your HVAC system, contact us at Sanalife to help you figure out what your ideal solution looks like for your building. 

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