HELP! I Have Something Crawling In My Vents, What Could It Be?

Rodent Guide
Written By Rodent Guide

I believe in treating all creatures with respect. My mission is to ensure everyone understands how to protect their home from rodents without using cruel methods.

Okay, first, calm down. If you hear crawling noises in your air vent or HVAC system, it is not something to panic about. In most cases, it probably is a rodent, insect, or other animal that got lured there due to the warmth.

However, it is essential to know what insects or animals are inside, if they can cause any damage, and how to get rid of them.

Here is what it could be:

What Could Be Crawling Around in Your Vents?

Animals in the vent system are a widespread problem, and it is not an indicator of your hygiene or cleanliness.

This problem is primarily relevant in the winter months as your ducts will be warmer than the outside, and visitors love the warmth.

These visitors are not limited to but include:

1. Mice

mice huddled together

These pesky little rodents happen to be the most common visitors to your HVAC system. Mice love fitting themselves into tight spaces, and they usually slip through the cracks in your ductwork or attic.

Mice in the HVAC are easy to detect as they make a very noticeable scratching sound, and you might even notice one around.

The biggest problem with mice in your air vents is that mice can chew through materials.

They can also create a nest with chewed pieces, grass, paper, and other dry objects and lay their offspring. This will turn into a significant problem down the line and is why you should try to get rid of them.

Rodents like mice can spread a large number of diseases (both directly and indirectly), so best get rid of them ASAP!

2. Rats

rat roaming on ledge, looking at camera

Rats are another common rodent that will find their way into your vents.

As you are aware rats, have an excellent set of teeth, and it won’t take long for them to destroy your attic storage space or wirings. Instead, rats can chew through many materials, so watch out for signs!

Rats will also leave their droppings everywhere, and some will even get stuck and die, creating an awful rotting dead rat smell that can last weeks.

3. Cockroaches

cockroaches near vent

Cockroaches have a unique body structure to fit through even minor gaps, preferring dark environments, so they may choose to nest in ductwork from time to time.

They don’t cause much harm, but you could notice them moving in the ductwork because they make a noise. Either way, because they have the potential to spread infections, you should avoid having them in your home at all costs.

4. Snakes

snake looking into camera

Okay, now we are getting serious. Many people fear snakes, and for a good reason, especially the venomous types!

When the temperature begins to cool, snakes seek warm places to hide. Because they are cold-blooded species, they cannot control their internal body heat.

Snakes tend to nest in ducts, which also means that they may be able to reproduce there. They may also wrap themselves inside condenser units due to their attraction to the heat generated by the system.

It is killed when the aluminum fins begin to turn, and based on the scale of the snake, it may cause damage to the fan blades or other elements of the heating system.

Although snakes are not going to be a problem in all parts of the world, it is generally a good idea to keep your home unfavorable to snakes. Instead, keep your lawn well-trimmed, look for tiny holes and fill them up as soon as you see them.

You can also use sulfur powder or carbonic acid as they are known to keep snakes away.

5. Spiders

black spider in web

Spiders, like cockroaches, are adept at wriggling their way into confined spaces. Because they are tiny, they may get into your pipes, vents, and interior air cooling unit if you do not keep those areas clean and maintained correctly.

Even though spiders do not cause harm to your HVAC system, they still pose a health threat because many spiders contain venom that is strong enough to cause injury to people.

Because most spiders, unlike cockroaches, have solitary lives, you may only have one or two invaders in your home. It is also easy to distinguish dangerous spiders from harmless ones. But, more often than not, if it looks like it can cause serious harm, that is the case.

If you’re concerned about extremely dangerous spiders, you should get advice from a professional.

6. Birds

bird perched on a wire

Like all other animals on this list, birds also come to your air vent looking for a safe, dry, and warm place to live. But the main issue here is not the birds themselves; it’s what they bring along.

If a bird chooses your HVAC system to build a nest and lay eggs, it will need to feed the baby birds. The favorite feast for them is insects and bugs, and before you realize your air duct will be filled with crawling insects that can spread diseases.

Another problem is that their nests will clog up the vents. It will stop any possible airflow, and your HVAC system will stop working as intended.

7. Squirrels and Raccoons

squirrel on a tree

Squirrels and raccoons are interchangeable with mice since they are also rodents and can cause the same problems.

During the winter months, squirrels will happily find a place in your home to settle down, including your vents.

How to Get Rid of Them

It is possible to remove an animal from an air duct. The simplest method is cleaning your air duct. You can do it yourself or hire a company to do it for you.

It is possible to clean the air duct at a certain distance, but the bulk of it is out of your reach. As a result, you’ll want to hire experts. But, at a fair price, they offer the greatest and most effective services.

Having a pet cat is also a somewhat effective method of getting rid of rodents, while you can also take rodent-proof ducting and extra precautions to avoid these issues.


Do you have something crawling in your vents? Now you know the 7 most common things it could be.

Regular maintenance is the key to keeping your vent system clean and safe from intruders. But you should not be scared as this issue is perfectly common and very easy to deal with methodically.

Just keep an eye out and contact professionals whenever you feel the need to.

Good luck!


About the Rodent Guide

I’m an expert in do-it-yourself rodent control. For more than 20 years, I’ve dedicated my life to helping people live harmoniously alongside these critters by sharing rodent control solutions that are effective and kind.

I believe in treating all creatures with respect. My mission is to ensure everyone understands how to protect their home from rodents without using cruel methods.

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