Sewage Smell Coming From Air Vents

Sewage Smell Coming From Air Vents

Your air vents are an important part of your home. They keep you cool in the summer, warm in the winter, and most importantly they ventilate and circulate the air you breathe in your house. So if your air vents start to smell like sewage, rotten eggs, or even poop, not only will living become unpleasant, but it could also be dangerous for your health.

What is that foul smell?

There are a number of different disgusting smells which can fill up your home through your air vents. Firstly, you must identify which smell you’re dealing with, before figuring out what to do about it. Here are some of the common smells you will encounter.

  • Mildew – this is one of the most common smells you can have coming from your air vents and can give off a musty, mouldy odour. It can also smell of stinky feet and these smells are mostly caused by the condensation of the cooling unit. When the drainage system is not working correctly, water can build up and the smell is born from the stagnant water.
  • Dead animals – sounds extreme, but it’s a fairly simple explanation. Small animals, such as birds, rats and mice, often get stuck in air vents or seek shelter there during the winter months and end up dying. It takes some time, but eventually, the corpse begins to rot and smell and whenever you turn your unit on you’ll smell it. The sooner you get rid of it, the better.
  • Sewage – if a noxious sewage smell begins to enter your home through your air vents, you need to get rid of that revolting smell. Not just because no one will want to come to your house, but also because long exposure can cause serious health problems, especially to your digestive system, with e.coli, salmonella and pinworms being some of the most common issues. 
  • Rotten Eggs – the smell of rotten eggs is almost as bad as the smell of sewage, but you won’t find any eggs if you go looking for the source of the stink. This smell is typical of a natural, colourless gas called hydrogen sulfide, and unlike the others, inhaling too much of this can lead to fatal consequences.

What is Hydrogen Sulphide?


Commonly known as sewer gas or swamp gas, which should tell you everything you need to know, this gas is flammable and can be very toxic depending on the level of exposure.

Effects of inhaling hydrogen sulfide can vary, from irritation of the eyes and lungs, headaches, dizziness and upset stomach, all the way to loss of consciousness and even death in extreme cases.  

Workers employed in oil and gas industries, the mining sector, paper processing and raynor manufacturing are most likely to suffer from exposure to hydrogen sulphide, so if you smell that rotten egg smell in your home, act fast!

So what can I do about these disgusting smells?

  1. If you believe the smell wafting through your air vents is mildew, then simple AC maintenance is required. Depending on how bad it is, you can do this yourself by gaining access to the filter and cleaning it out. You should also remove the vent, and wipe down all the surfaces with an all purpose cleaner. You may find standing water, which you should get rid of, but this would suggest there is a problem with the filtration system, in which case a call to the pro’s would be needed. Don’t forget to clean the vent’s themselves as these collect dust and dirt and can add to the problem.
  2. If there is a growing rotting smell you can sense, which gets stronger whenever you turn your cooling and heating unit on, then you’re most likely looking for a dead animal. Though unpleasant, this is a simple search and remove job. Gain access to the unit and vents, grab a torch, some gloves and a broom, and follow the smell. Once you find the carcass, safely remove it and get rid of it, and give the whole area a clean with a disinfectant. If the smell continues after this, it might be time to give the air conditioning company a call to come and take a look.
  3. The sewage smell is a bit tricky to handle and it’s very rare you can take care of it yourself, unless you’re a plumber by trade of course. The smell coming through your air vents is actually methane, which is a hazardous gas, so act immediately if poop is what you smell. The problem is most likely to come from either a ruptured sewer pipe, or a backed up sewer line. This smell is often common if you have a septic tank odor, but don’t worry, we have you covered for that as well.
  4. When rotten eggs start invading your nostrils and home, there’s not much you can do except to call an expert immediately! If the smell is very strong, take extra precautions by opening the windows, turning off the gas and water supply, and leaving your home. Only return when a professional arrives and do as they tell you.


Man Is Fixing Air Vent At Home

How do I maintain my air conditioning unit?

Air conditioning units can seem intimidating with all the big machinery and mechanical parts, so it’s easy to simply ignore it, but some simple, DIY,  maintenance steps will avoid a whole host of potential problems in the future.

From time to time, from one to six months, change your air filter. This will also mean you and your family breathing in cleaner air! Remove and clean the air vents which trap dirt every few months. All you need is some warm water, washing up liquid and a brush. Finally, schedule an appointment with your AC maintenance company and avoid these problems altogether!

Why do my water appliances stink of sewage?

If the smell of poop is coming through your air vents, it’s quite likely it’s going to impact all the pipes in your home. Anything connected to these pipes will release this noxious order. So yes, you guessed it, your washing machine, and your dishwasher will smell the same, so you better have your plumber on speed dial!