Indoor Air Quality – IAQ
Indoor Air Quality – IAQ Blog
Indoor Air Quality – IAQ Blog
How Safe Is Your Indoor Air Quality?
Indoor Air Quality – IAQ
Indoor air quality (IAQ) has become one of the most important topics in the HVAC industry. In the past, the focus of HVAC design was simple comfort—primarily maintaining temperature. Today, we understand that temperature is only one piece of the comfort and safety equation.
According to research published by PubMed.gov, most illnesses linked to environmental exposure originate indoors. When you consider the cumulative time people spend at home, at work, and in other enclosed spaces, IAQ becomes a critical component of long-term health.
What Affects Indoor Air Quality?
Poor IAQ is more than just “stale air.” Buildings can accumulate a wide range of contaminants, including:
- Cleaning solvents
- Paints and chemicals
- Pesticides
- Carbon dioxide (CO₂)
- Volatile organic compounds (VOCs)
- Radon gas
- Off-gassing from furniture, carpet, and building materials
- Fumes from attached garages
These contaminants can contribute to:
- Eye, nose, or throat irritation
- Headaches
- Drowsiness or fatigue
- Allergic reactions
- Asthma triggers
- Reduced cognitive function
- Over the long term, even serious health risks
Simple Solutions You Can Start With
Basic maintenance and proactive habits can dramatically improve IAQ.
Replace air filters regularly
Dirty filters restrict airflow and recirculate contaminants.
Use air purifiers or room air cleaners
Especially helpful for allergy or asthma sufferers.
Consider UV germicidal lamps
UV-C technology helps neutralize airborne pathogens.
Maintain your HVAC system
Inspection and cleaning of ducts and equipment can reduce:
- Dust buildup
- Mold
- Potential carbon monoxide leakage (in gas furnace applications)
These steps are cost-effective and provide immediate benefits.
IAQ in the Context of COVID-19 and Other Infectious Aerosols
The COVID-19 pandemic highlighted the importance of indoor ventilation. Organizations like ASHRAE—the American Society of Heating, Refrigerating, and Air-Conditioning Engineers—provide standards and recommendations to improve IAQ during infectious disease concerns.
ASHRAE Standard 62 specifies minimum fresh air ventilation rates, ranging from 15 to 60 CFM per person, with most facilities falling within the 15–35 CFM per person range.
In April 2020, ASHRAE released their Position Document on Infectious Aerosols, noting:
“The risk of pathogen spread… can be affected both positively and negatively by the airflow patterns in a space and by HVAC and local exhaust systems.”
In other words, your HVAC system can either help mitigate pathogen spread—or worsen it—depending on design and operation.
The Role of Economizers
For commercial buildings, economizers provide a controlled method of introducing fresh outdoor air. During favorable conditions, they allow “free cooling” by using outdoor air instead of mechanical cooling.
ASHRAE guidance for infectious aerosol control recommends:
- Increasing outdoor air ventilation
- Disabling demand-control ventilation where outdoor air is needed
- Operating systems for extended hours
However, operating with 100% outdoor air is not always feasible. Most rooftop units are not sized to handle extreme heating or cooling loads when conditioning full outdoor air continuously. Running in this mode 24/7 can drive energy costs to astronomical levels.
A balanced approach is needed:
- Increase fresh air when possible
- Avoid overloading HVAC equipment
- Maintain control of temperature and humidity levels
Energy Recovery Ventilation (ERV) Considerations
Although MicroMetl no longer manufactures ERVs, understanding their role helps contractors and building operators make informed decisions.
ERVs can:
- Exhaust stale indoor air
- Recover heat or cooling energy from that air
- Reduce the load on rooftop units
- Improve humidity control
However, ERV systems must be evaluated carefully when infectious aerosol concerns are present.
Airstream cross-contamination—called Exhaust Air Transfer Rate (EATR)—can allow small amounts of exhaust air to recirculate into the supply air. Some ERV technologies allow up to 5–10% EATR under certain conditions, which is acceptable under ASHRAE 62.1 for general ventilation but may not be appropriate during health-related situations.
When addressing infectious aerosols, ASHRAE advises:
“Bypass energy recovery ventilation systems that leak potentially contaminated exhaust air back into the outdoor air supply.”
Bypassing an ERV can create its own challenges, especially if the rooftop unit was sized with the ERV’s energy recovery in mind. This reinforces the importance of proper design and ongoing evaluation—not simply replacing equipment at face value.
Control CO₂ Levels for Better IAQ
CO₂ levels are an effective indicator of ventilation adequacy in occupied spaces. Elevated CO₂ can cause:
- Drowsiness
- Reduced concentration
- Headaches
- Increased fatigue
Here are common CO₂ exposure ranges:
| CO₂ Level | Impact |
|
<1000 ppm |
Acceptable (ASHRAE recommendation) |
|
1000–2500 ppm |
Impaired judgment, reduced cognitive performance |
|
2500–5000 ppm |
Cognitive dysfunction, headaches |
|
60,000 ppm |
Hearing and visual disturbances |
|
70,000 ppm |
Life-threatening |
Demand-control ventilation strategies that rely on CO₂ sensors can help maintain safe levels, especially in:
- Classrooms
- Meeting rooms
- Gyms
- Auditoriums
Final Thoughts
Indoor Air Quality directly impacts comfort, health, and productivity. The keys to maintaining healthy IAQ include:
- Adequate ventilation
- Proper filtration
- Regular maintenance
- Monitoring CO₂ and VOC levels
- Using HVAC systems intelligently and efficiently
HVAC professionals should stay informed of evolving standards and educate building owners about the importance of IAQ and its direct effect on energy costs, health, and occupant comfort.
How Safe Is Your Indoor Air Quality – IAQ
Once Upon A Time… Comfort of temperature was the primary goal of the HVAC Industry. According to the website PubMed.gov, “Most illnesses related to environmental exposures stem from indoor air exposure”. Couple a home’s poor IAQ with your workplace and the result could be devastating to your mental and physical health. How safe is the Indoor Air Quality in your home or office space?
The core of the problem with Indoor Air Quality goes beyond the recycling of stale air. Sources of contaminants include cleaning solvents, paints, pesticides, CO2, building materials, radon gas, garages, even carpeting & furniture to name a few. These contaminants can cause a range of effects. Some exposures range from eye, nose, and throat irritation, to headaches, allergic reactions, even mortality.
Simple Solutions
Replace your air filters in a timely manner and consider room air cleaners, air purifiers, or UV lamps. Have your ductwork periodically cleaned and your HVAC system maintained to prevent carbon monoxide leakage should you have a gas furnace. Simple maintenance and room devices can remove or neutralize triggers for asthma or allergy sufferers. These simple low cost measures can go a long way to improve the safety & air quality of your home or office and the well-being of your family and coworkers.
COVID-19 & Pandemic Concerns. 
Global pandemics such as COVID-19 raise new concerns. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) is a professional association seeking to advance heating, ventilation, air conditioning & refrigeration systems design and construction. ASHRAE provides guidelines for IAQ. ASHRAE Standard 62 – Ventilation for Acceptable Indoor Air Quality specifies minimum ventilation rates and indoor air quality acceptable for indoor occupancy… with the intention to minimize the potential for adverse health effects.
Early in April 2020, ASHRAE offered a study titled; ASHRAE Position Document on Infectious Aerosols. This study directly addressed COVID-19 and noted; “The risk of pathogen spread, and therefore the number of people exposed, can be affected both positively and negatively by the airflow patterns in a space and by heating, ventilating, and air-conditioning (HVAC) and local exhaust ventilation (LEV) systems”.
ASHRAE recommends that a portion of outside air must be introduced into a commercial building to maintain a healthy indoor air environment… But is it enough with the threat of pandemics?
ASHRAE 62 Recommended Minimum Outdoor Air Requirement
- 15 to 60 Cubic Feet Per Minute (CFM) Per Person
- Most Common Range is 15 to 35 CFM Per Person
- The Average Range is 15 to 20 CFM Per Person
ASHRAE’s thought on patients infected with COVID, a 100% full exhaustion of air is recommended. However, what’s the cost?
Is An Economizer The Solution?
The ASHRAE Study recites for non-healthcare buildings… “Increase outdoor air ventilation (disable demand-controlled ventilation and open outdoor air dampers to 100% as indoor and outdoor conditions permit)”, and “Keep systems running longer hours (24/7 if possible)”. An Economizer should be in every Rooftop Unit (RTU) in my opinion. They are necessary to effectively maintain the ASHRAE minimal fresh air requirements while offering free cooling with an optimal outdoor Temperature and Humidity range. To disable them when “Outdoor Conditions Permit” means they must be re-engaged when those conditions are no longer favorable. High humidity and extremes in temperature are problematic. Most HVAC RTU’s are not designed to handle the heating & cooling load required to condition these extremes with 100% outside air. Additionally, the cost of a 24/7 remedy under such circumstances would lead to astronomical power consumption costs to the building owners.
If you have an Economizer installed, you can set it to increase the outdoor air change rate. The change rate is described as how many times per hour you completely remove the inside air withing a space and replace it with fresh outside air.
The Energy Recovery Ventilation (ERV) Solution
An ERV allows you to remove stale, perhaps unsafe air from a building while recovering the heating or cooling with high-efficiency. Therefore, when the temperature outside is at zero degrees Fahrenheit, and 70 degrees inside, at an 80% ERV efficiency on temperature, the ERV will return 56 degrees to your RTU. An ERV coupled with a rooftop unit can significantly reduce the outside air load, which allows you to reduce the cooling and heating capacity of the RTU, offsetting the investment cost of an ERV.
Should ERV airstream cross-contamination be a concern? When the airstreams cross inside an ERV, there is a potential for the building’s exhaust air to leak through to the fresh outside supply air and return back into the building or space. AirXchange, the manufacturer of ERV wheels and cores (the critical transfer component in all of MicroMetl’s Engineered ERV products) and the manufacturer of choice for MicroMetl, states… “Some ERV units or sections are designed to allow for as much as 5% or 10% Exhaust Air Transfer Rate (EATR). This is within ASHRAE Standard 62.1 allowances and is the most energy-efficient for some spaces”.
ASHRAE is not a fan of this situation when addressing indoor spaces from infectious aerosols (Such as COVID-19) according to the April 2020 documentation. ASHRAE states “Bypass energy recovery ventilation systems that leak potentially contaminated exhaust air back into the outdoor air supply.” Bypassing the ERV can present a new set of issues if your RTU was down-sized when coupled with and ERV to meet the building’s load. So the new goal or solution is to prevent cross-contamination, and not bypass your ERV investment and overburden your RTU.
The subject of cross-contamination is a topic for another article. If you are a MicroMetl approved customer, you have access to our Online ERV Builder. The software offers the EATR information for each selection and allows you to inject alternatives to change that variable. Otherwise, contact MicroMetl’s Customer Service or Sales Representative to tailor an ERV to your specific needs. We can reduce and/or eliminate cross-over.
Control Those CO2 Levels
We’ve all experienced that lethargic moment when inside a room with poor ventilation when no amount of coffee can keep you awake. Elevated CO2 Levels can cause mild to dangerous physiological & mental conditions at varying levels, but can be controlled.
The Effects of CO2 Concentration
- ASHRAE Recommends Indoor Levels of Less Than 1.000 Parts Per Million (PPM) of CO2
- 1000 PPM In Under 2.5 Hours – Impairs Judgement, Decision Making & Thinking Skills On A Short Term Basis
- 2500 PPM In Under 2.5 Hours – May Render People Cognitively Marginal or Dysfunctional
- 5000 PPM – Headaches, Lethargy, Mental Slowness, Emotional Irritation & Sleep Disruption
- 60,000 PPM Within One – Two Minutes – Hearing & Visual Disturbances
- 70,000 PPM In Five Minutes – Death
CO2 monitors can be added to multiple MicroMetl products to maintain safe CO2 levels. Add them to an Economizer with Power Exhaust, or an ERV for on-demand control. Again, contact our expert Sales Staff & Customer Service department for your best solution.
MicroMetl encourages your comments and recommendations. Thank you for supporting MicroMetl!
