Is It OK to Cover a Floor Vent with a Rug? (Fully Explained)

Floor vents are integral to proper air conditioning.

In line with the law of Physics – hot air rises, cold air settles – floor vents are more effective in heating functions than cooling.

They often accompany a centrally located (beneath the floor) furnace so that gravity can play a role in air circulation.

So, Is It OK to Cover a Floor Vent with a Rug?

The short answer to that question is “No.” It’s bad for both your furnace and air conditioner and can pose a safety risk.

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Is It Ok To Cover A Floor Vent With Furniture?
Is It OK to Cover a Floor Vent with a Rug?
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But, In What Situations Would You Cover Your Floor Vents?

There are several of them, one of them being preventing your day-to-day floor debris from ending up in the ductwork beneath the floor.

To Prevent Accidents

Vent-related accidents are quite common.

Curious kids and pets can end up with fingers and paws stuck in the grill.

This is more likely with most commonly used vents that fall in these two size groups:

  • 2 – 1/4″X10″ 
  • 8″X14″ (which has four subgroups 4″X10″, 4″X12″, 6″X10″, and 6″X12″).

There’s also a significant risk of dropping unwanted items such as coins by accident into the vent.

If these items are left in there, they may block the ductwork and demand a costly repair.

Vents Are In Inconvenient Spot

Another reason why you might go down this perilous route is if your vents are located on an inconvenient spot that must either be covered by the rug or accommodate a piece of furniture.

There’s only one situation in which you’d cover your floor vents without worry – when your furnace/air conditioner is inactive.

Why Is It a Bad Idea to Cover Your Floor Vents?

You probably know by now that your HVAC unit relies on the supply vents – whether wall-based or floor-based – to deliver one or two of the following types of air:

Hot Air

If your supply vents connect to a furnace

Cool Air

if your air conditioner serves your room in the summer via floor vents

You can as well use it to control the humidity of the room.

With that said, if the air vents are blocked, that particular section of the floor is more likely to get very hot, cold, or humid depending on its purpose.

So here’s why you should avoid obstruction at all costs:

#1. Blocked Supply Vent Increases the Chances of Furnace-Induced Home Fire

Obstructed vents, more so supply vents, can cause the furnace to malfunction and start a fire.

Furnace-induced home fires are more common than you may think.

There are two types of vents, by the way – supply and return vents.

Supply vents deliver the fresh conditioned air into the room while return vents suck the stale air and direct it into the machine for conditioning.

A typical furnace comes with a heat exchanger in form of a metal coil.

It’s tasked with receiving regular air, heating it, and pumping the warm air into the ductwork and finally out of the vents with the aid of blowers.

Blocked vents in this situation may mean two things – the warm air is being forced to stay where it shouldn’t stay and the blower is being overworked.

In the long run, the hot air may build up, heat the ductwork and the rest of the furnace system, and start a fire.

The NFPA recognizes the HVAC system as one of the top causes of home fires.

  • About 3 percent of home fires are directly attributed to air conditioners.
  • Another 3 percent is caused are caused by clothes dryers.

Clearly, you have bigger things to worry about because, about half (50 percent) of home fires have something to do with electrical distribution, power transfer equipment, and lighting which almost always involve electrical malfunction or failure.

Cooking equipment contributes 15 percent, heating equipment 9 percent, and fans 6 percent.

#2. The Potential Mold Problem

Mold will grow anywhere damp, especially in places with very little or no activity.

Blocked floor-based supply vents retain much of the conditioned air close to the floor, creating a great environment for the growth of mold.

While conditioned air is seldom humid, the mere fact that it’s cold is enough to encourage the growth of mold.

More mold can grow if the musty environment spreads onto the fabrics that make your rug.

The presence of mold in indoor settings can be uncomfortable to some people and devastating to others.

For the least vulnerable, exposure to mold often leads to symptoms like stuffy nose, reddish/itching eyes, and wheezing.

The most vulnerable may deal with mold allergies and asthma in severe cases.

The issue with mold growth within your vents is not the effect it has on your health but the fact that it builds up slowly over a long time, meaning you are likely to discover it when you’ve already been exposed.

Also, conditioned air carries very little or no humidity, meaning it inflicts a drying effect on almost everything it comes into contact with.

If you ever left your AC machine running overnight and woke up with drier skin and eyes, that was it.

Floor vents blocked by furniture or carpet hold back the cold air, allowing the drying effect to take a toll on your items and cause discolorations.

#3. May Render Your Air Conditioner or Furnace Inefficient and Drive Up Your Electricity Bills

The air conditioner/furnace is inefficient if you are receiving less and spending more to run it.

For instance, the conditioner’s efficiency is calculated by the EER (energy efficiency ratio) which is basically the ratio of your device’s cooling capacity (measured in BTUs – British thermal units – per hour) to its power input (measured in watts).

EER = AC system’s cooling capacity / power consumed

As you can conclude, a higher EER rating means your air conditioner is more efficient.

There are many obstacles to running your furnace/air conditioner at their highest efficiency, one of those obstacles is blocked vents.

Blocked supply vents can completely or partially cut off the supply of conditioned air into the room, meaning a big part of your cooling/heating costs is going to waste.

Blocked return vents create the same problem because it would mean your furnace or air conditioner is deprived of the air, causing it to overwork or waste energy.

So What Should You Do to Blocked Vents?

It’s easy – unblock them. If you must place furniture over them, say, you’re deprived of room for your essential items, consider adding vent deflectors.

These are designed to collect or eject air sideways rather than perpendicularly and directly on the obstacle.

If the floor is made of wood, relocating your vents can be easier and less costly compared to ruining your HVAC system and having it repaired or replaced.

If your furnace or air conditioner is located in all places except beneath the floor, consider relocating your floor vents to the wall or ceiling.


To summarize everything, it’s a bad idea to obstruct your floor vents with a rug for these reasons:

  1. Risk of fire: blocked furnace vents causes the hot air to build up and can be significant enough to start a fire
  2. Inefficiency: blocked vents means you’re receiving less from the furnace or AC machine
  3. Potential mold growth: if the vents are supposed to deliver cold air, the ductwork behind them will certainly get musty and moldy.