November 2024
By: Josh Walejewski
Read Time: 3-4 Minutes
Our technicians have shared some truly astonishing stories over the years. Often complete with shocking photos of unexpected encounters in the field. Imagine the look on a technician’s face during a routine maintenance call when they removed a furnace panel and discovered a dead crab inside!
While it sounds unbelievable, animals—from mice and snakes to birds and, yes, even crabs (likely someone’s pet or would-be dinner), often seek warmth and shelter inside HVAC systems as temperatures drop. Unfortunately, their presence can lead to significant damage and safety concerns.
In this blog, we’ll detail why animals are drawn to HVAC systems, how they get in, the risks they pose, and steps to take to keep them out. With simple measures, you can protect your investment and avoid unexpected visitors in your comfort system.
Why Do Animals Get into Our Heating and Cooling Systems?
Many animals have keen senses that help them detect and locate sources of warmth. During colder months, their survival depends on finding environments that offer protection from the elements and freezing temperatures. The heat generated by HVAC and plumbing equipment can seem like the perfect place for critters seeking refuge to call home. Additionally, the enclosed spaces within HVAC systems offer security from predators.
How Do Animals Typically Get Inside?
Animals and pests can infiltrate HVAC systems through a variety of unnoticed entry points around your home. Common access routes include intake and exhaust vents or pipes that lack proper screening. Missing or damaged screens provide an open door for small creatures and insects. Dryer vents, kitchen and bathroom exhaust fans, and fresh air intakes are also prime entry points.
Similarly, open or unprotected chimney flues offer ideal nesting sites for birds and bats, allowing them easy access to your home’s interior and HVAC system. Attics and crawlspaces connected to your ductwork become vulnerable when exterior barriers are compromised. This makes it easy for animals to enter the HVAC system from within your home.
Lastly, poorly sealed gaps around refrigerant lines, pipes, and wires can create small openings that rodents and insects exploit to gain entry. These gaps might seem insignificant, but they’re often more than sufficient for determined pests.
For example, a mouse can fit through a hole about the size of a pencil—approximately 1/4 inch in diameter. Mice have long, flexible bodies and lack collarbones, allowing them to squeeze through openings as small as their heads. Similarly, bats can fit through holes as tiny as 3/8 inch in diameter—about the size of a dime—according to Bat Conservation International.
Common HVAC Visitors and Their Risks
Rodents
Mice, chipmunks, and squirrels are notorious for gnawing on components such as electrical wires, circuit boards, and insulation. They often enter and get stuck inside intake and exhaust pipes.
When these pipes are blocked, it can cause potential fire hazards, carbon monoxide risks, and system breakdowns. Rodent droppings and urine can also cause unwanted odors and increase the risk of illness among occupants.
Snakes
Snakes in your HVAC system pose two main risks. First, if a snake coils around a stationary component like a fan, it can get caught and damage the equipment when the system starts, leading to costly repairs.
Second, snakes typically won’t survive inside your ductwork. As they begin to decay, they can emit unpleasant odors and pose health risks.
Birds & Bats
These pests often build nests in vents or ducts, causing blockages that reduce airflow and efficiency; the nesting materials can also become fire hazards. Additionally, their droppings can accumulate, leading to unsanitary conditions and health risks. Decomposing birds or bats can emit unpleasant smells and contaminate indoor air quality.
Insects
A wide range of insects might enter your home through your HVAC and mechanical systems. Insects such as carpenter ants and termites could lead to potential structural damage to your home. Bees and wasps in your home present many risks such as people getting stung or their nests blocking intake or exhaust pipes.
Exotic Pets
Exotic pets like lizards, hermit crabs, or other small creatures that escape their enclosures may seek out the warmth of your HVAC system. If they enter the ductwork or equipment, they can cause blockages and strain the system.
These pets are unlikely to survive long outside their enclosures, leading to nasty odors, health risks, and reduced indoor air quality.
Prevention Tips
Enroll in a Preventative Maintenance Plan: Having a preventative maintenance plan lets professionals spot early signs of animal intrusion before they turn into major issues. Regular inspections of outdoor units ensure that protective screens and seals are intact, preventing animals from entering and causing damage or health hazards.
Check Screens on Venting: Outdoor vents and intakes typically have screens to prevent animals and other pests from entering. Check to ensure the screens aren’t missing or compromised .
Use an AC Topper Instead of a Full Cover: Toppers are a better choice, as most debris enters your outdoor unit through the top. Full covers create a welcoming and warm place for mice and other pests to call home during the cold months.
Seal Any Gaps: Visually inspect any ductwork that vents outside for gaps or cracks that need to be sealed.
Control Surrounding Vegetation: Animals are more likely to approach outdoor HVAC units if shrubs or plants provide easy cover. Keeping vegetation trimmed back reduces hiding spots for pests.
If you’re experiencing issues with insects, you can also plant bushes or shrubs that are natural deterrents. Some plants to consider include peppermint, chrysanthemums, marigolds, garlic, and yarrow. Just be sure to leave at least 3 feet of space around your outdoor unit to maintain optimal airflow.
What to Do If You Discover an Animal in Your HVAC System
If you find an animal in your HVAC system, safety should be your top priority. Avoid attempting to remove the animal yourself, as doing so without proper tools or knowledge can pose risks to both you and the creature. The first step is to shut off your HVAC system. This prevents any harm to the animal from moving parts like fans or motors and protects your equipment from potential damage.
Next, contact a professional—either an HVAC technician or a licensed pest control expert—to handle the situation safely and humanely. They have the expertise to remove the animal without causing injury and can assess any damage that may have occurred.
If the animal is deceased, it’s especially important to have professionals handle the removal. Additional cleaning and disinfecting might be necessary to eliminate health hazards and unpleasant odors. Prompt action ensures your HVAC system remains in working order and that your home’s air quality is maintained.
Conclusion
By understanding why animals are attracted to your HVAC system and taking proactive steps to prevent their entry, you can protect your home’s comfort and safety. Simple measures like regular maintenance, sealing gaps, and monitoring your system can make a significant difference. Keep your HVAC system critter-free and enjoy peace of mind throughout the seasons.
Read more blog posts from Kettle Moraine Heating & AC.
About the Author
Josh Walejewski
Josh is a professional marketer who has worked in the HVAC industry since 2017. With a Bachelor of Applied Arts and Sciences Degree (B.A.A.S) in marketing and sustainable business management from the University of Wisconsin, he has a passion for all aspects of HVAC, business, marketing, and environmental stewardship.
