Houston AC: Mold Lies Stealing Summer Glow?

By Franklin Everett Shaw

January 10, 2026

The air in your Houston home feels heavy, thick, and just wrong. You’ve noticed a musty odor, and maybe even some dark spots appearing on your walls or, worse, near your AC vents. It’s a scenario all too familiar to Houston residents: mold growth, often fueled by our city’s relentless humidity and, unfortunately, sometimes exacerbated by our air conditioning systems. But don’t panic. This guide is your roadmap to identifying, testing for, and dealing with mold in your AC unit, specifically tailored for the unique challenges of living in Houston.

First, let’s talk about why your AC is a prime suspect. Air conditioners, by their very nature, create condensation. This moisture, combined with dust and organic matter that inevitably finds its way into the system, creates the perfect breeding ground for mold. In Houston, the already high humidity levels amplify this problem, making AC units a haven for mold spores.

So, how do you know if you have a problem? Look for these telltale signs:

A persistent musty or earthy odor, especially when the AC is running.
Visible mold growth around vents, on the AC unit itself (indoor or outdoor), or in the drip pan. Mold can appear in various colors, including black, green, white, or brown.
Allergy-like symptoms, such as sneezing, coughing, runny nose, itchy eyes, or skin rashes, that worsen when the AC is on.
Water stains on ceilings or walls near AC vents.

Now, let’s get to the testing. While professional mold testing is always recommended for a comprehensive assessment, there are DIY methods you can use to get a preliminary indication of mold presence. Keep in mind that these tests are not definitive and should not replace professional evaluation, especially if you suspect significant mold contamination.

Here’s a simple DIY mold test you can perform:

Gather your supplies: You’ll need clear tape (like Scotch tape), a clean cotton swab, a clear plastic bag, and a magnifying glass.
Visually inspect: Carefully examine the areas around your AC vents, the unit itself, and the drip pan for any visible mold growth. Note the location and appearance of any suspected mold.
Tape test: If you see visible mold, gently press a piece of clear tape onto the surface. Make sure to get a good impression.
Swab test: If the area is difficult to reach with tape, use a slightly damp cotton swab to gently wipe the surface.
Seal and label: Place the tape or swab into a clear plastic bag and seal it tightly. Label the bag with the date, location of the sample, and a brief description (e.g., “AC vent, black mold”).
Incubate (optional): For a more conclusive DIY test, you can incubate the sample. Place a damp paper towel in a separate sealed bag. Then, place the bag containing your sample inside this larger bag, but do not let the sample bag touch the damp paper towel. Keep the bag in a warm, dark place for 2-3 days. Observe for any mold growth.
Examine: Use a magnifying glass to examine the tape or swab for signs of mold growth. Look for small, fuzzy, or powdery colonies.

Important Considerations for Houston Homes:

Attic AC Units: Many homes in areas like Katy and Sugar Land have AC units located in the attic. These spaces are prone to extreme temperature fluctuations and humidity, making them particularly susceptible to mold growth. Exercise extreme caution when inspecting attic AC units, as temperatures can be dangerously high.
Ductwork: Mold can also grow inside your AC ductwork, which is difficult to inspect visually. If you suspect mold in your ducts, consider hiring a professional duct cleaning service with mold remediation capabilities.
Window Units: While less complex than central AC systems, window units in older Houston homes (like those in the Heights or Montrose) can also harbor mold. Pay close attention to the back of the unit, where condensation tends to accumulate.

What to Do If You Find Mold:

If your DIY test suggests the presence of mold, or if you have any of the symptoms mentioned earlier, it’s crucial to take action.

Professional Mold Testing: Contact a certified mold inspector in the Houston area. They can conduct a thorough assessment of your home and AC system, identify the type of mold present, and determine the extent of the contamination.
Mold Remediation: If the mold infestation is significant (larger than 10 square feet), it’s best to hire a professional mold remediation company. They have the expertise and equipment to safely remove the mold and prevent it from returning.
AC Maintenance: Regardless of whether you find mold, regular AC maintenance is essential for preventing future problems. Schedule annual AC tune-ups with a qualified HVAC technician. Ask them to specifically inspect for mold growth and clean the system thoroughly.

Houston-Specific Resources:

Texas Department of Licensing and Regulation (TDLR): Verify that any mold assessment or remediation company you hire is licensed by the TDLR.
Better Business Bureau (BBB): Check the BBB rating and reviews of mold remediation companies in Houston.
Local HVAC Companies: Many HVAC companies in Houston offer AC cleaning and mold prevention services. Get quotes from several companies and compare their services and prices.

Legal Considerations for Renters:

If you’re renting an apartment in Houston and suspect mold growth in your AC unit, you have rights. Texas law requires landlords to maintain a safe and habitable living environment.

Notify your landlord in writing: Document the mold problem and request that they take action to remediate it.
Keep records: Keep copies of all communication with your landlord, as well as any photos or videos of the mold.
Consult with a lawyer: If your landlord fails to address the mold problem, consult with a lawyer specializing in tenant rights. You may have legal options, such as breaking your lease or suing for damages.

Preventative AC Maintenance in Houston’s Humid Climate:

Prevention is always better than cure. Here are some tips for preventing mold growth in your AC unit:

Regularly change your AC filter: This helps to remove dust and debris that can contribute to mold growth. Change your filter every 1-3 months, or more often if you have pets or allergies.
Keep your AC unit clean: Wipe down the exterior of your AC unit regularly with a damp cloth. Clean the drip pan with a bleach solution (1 part bleach to 10 parts water) every few months.
Ensure proper drainage: Make sure that your AC unit’s condensate drain line is clear and flowing properly. A clogged drain line can lead to water buildup and mold growth.
Control humidity: Use a dehumidifier to reduce humidity levels in your home, especially during the summer months.
Run your AC regularly: Running your AC helps to keep the system dry and prevent mold growth. Even when the weather is mild, run your AC for a few hours each day.

Dealing with mold in your AC unit can be a frustrating experience, but by taking proactive steps to identify, test for, and prevent mold growth, you can protect your health and your home. Remember to utilize the resources available to you in the Houston area and don’t hesitate to seek professional help when needed. Breathe easy, Houston.