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Your HVAC system plays a significant role in indoor air quality (IAQ). Forced air can circulate allergens, pollutants, and contaminants already present in your home. While HVAC systems primarily filter air to protect internal components, they can also help improve IAQ when equipped with the right filters. In this article, we’ll explore how HVAC filters affect air quality and how to choose the right filter for your needs.
How HVAC Air Filters Work
HVAC air filters are installed in the system’s return air ductwork, where air is drawn into the system. From there, air flows into the furnace or AC air handler. As the system’s blower pulls air through the filter, airborne particles like dust, lint, and pet hair get trapped.
The primary purpose of HVAC filters is to prevent dust and debris from entering the furnace or air handler, which helps maintain system efficiency and longevity. Without a filter, dust buildup can cause wear on internal parts and force the system to use more energy.
While standard HVAC filters reduce dust circulation, smaller particles like pet dander, mold spores, chemical fumes, and certain pollen types may still pass through lower-rated filters.
An Overview of Air Filter Ratings
Choosing a higher-rated filter can help improve air quality by capturing more airborne contaminants. The most widely used rating system is the MERV (Minimum Efficiency Reporting Value) scale, which measures how effectively a filter traps particles of different sizes.
- MERV 1–4: Basic filters that trap larger particles like dust and lint. Not very effective for IAQ improvement.
- MERV 5–8: Common in residential HVAC systems, capturing dust, pollen, and mold spores.
- MERV 9–12: Captures finer particles like pet dander and some bacteria, improving IAQ for allergy sufferers.
- MERV 13: Considered the highest practical rating for most residential HVAC systems. Traps bacteria, smoke, and finer dust.
- MERV 14–16: Typically used in hospitals and specialized commercial settings, not standard for home HVAC systems.
If you see 1-inch residential filters labeled as “good,” “better,” and “best”, they usually correspond to:
- Good (MERV 6–7) – Basic dust and lint protection.
- Better (MERV 8–10) – Helps reduce allergens like pollen and mold spores.
- Best (MERV 11–13) – Traps finer particles, improving IAQ significantly.
While media filters (4-5 inches thick) can be MERV 11–13, residential HVAC systems generally do not support MERV 15 filters, which are typically used in specialized commercial applications.
How to Know Which HVAC Filter to Use
If you’re unsure which filter is best for your HVAC system, consult a certified technician. Using a filter that’s too restrictive for your system can reduce airflow, increasing strain on the blower motor and decreasing efficiency.
- Older HVAC systems may struggle with anything above MERV 8.
- Many modern systems can handle MERV 11–13 with proper airflow adjustments.
- MERV 14+ filters are usually not recommended for standard residential HVAC systems.
If your main goal is HVAC protection, a MERV 6–8 filter is usually sufficient. If you have allergies, asthma, or other respiratory concerns, a MERV 9–13 filter may be a better choice. Keep in mind that higher-rated filters clog faster, requiring more frequent replacement to maintain efficiency.
If your system cannot support a high-MERV filter but you need better IAQ, consider installing a whole-home air filtration system or air purifier instead of overloading your HVAC system.
Replacing Your HVAC Air Filter Regularly
Most HVAC manufacturers recommend replacing disposable air filters every 1–3 months, depending on factors like:
- Pets – Homes with pets should replace filters more frequently.
- Allergies or respiratory conditions – Consider checking filters monthly.
- Climate – Homes in dry, dusty areas may need replacements more often.
- System usage – HVAC systems running continuously (e.g., in hot summer months) will clog filters faster.
Some smart thermostats and newer HVAC systems do provide filter replacement reminders, but if your system doesn’t, it’s a good idea to set a reminder on your phone or calendar.
A clogged air filter reduces airflow, forcing your system to work harder. This results in:
- Reduced heating and cooling performance
- Longer system cycles and higher energy bills
- Increased wear and tear, leading to more frequent repairs
Skipping regular filter changes is one of the top reasons HVAC systems fail prematurely, so keeping up with replacements can help extend the life of your unit.
Our Experts Can Help
When it comes to air conditioning, heating, indoor air quality, and plumbing in the Dallas-Fort Worth area, On Time Experts is ready to help. We’ve been in business since 1981 and offer expert guidance on air filters, whole-home filtration, and air purification solutions. If you’re unsure which filter is best for your home or need professional IAQ solutions, give us a call today!
