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What is an Air Register?

By Sheri Cyprus
Updated: May 17, 2024

An air register is the cover on a duct. A duct system channels heated or cooled air, while the register controls the distribution of it into each room. Air ducts are hollow metal tubes. Air registers that fit onto one end of each duct are also usually made of metal, although some are plastic or wood. An air register usually has horizontal and/or vertical slatted openings; their direction and width determine how the heated or cooled air is distributed.

The slatted openings in air registers are called linear slots by manufacturers. Some air registers have one direction of slats or slots, while others are multi-directional. Some rectangular types of air register often have little levers located at the bottom of closable slats set in different directions. This format allows different sections of slats to be opened or closed to allow more or less air flow into a room. One-piece air registers with stationary rather than movable openings are usually sold as grilles or grills.

Grill or grille air registers are typically made of wood or metal. Many of these have wide, square holes rather than linear slats or slots in order to distribute a larger air flow. A wooden air register is the ideal choice for a duct located on a wood floor. Stainless steel or aluminum air registers may blend better on gray stone or slate floors. The different materials, colors and finishes of air grilles and registers allow home designers to create cool or warm looks to suit specific decors.

Many registers are rectangular in shape, but a type of air register called a diffuser is often circular. Diffusers spread out the air around the room, while slatted registers release it in streams. Diffusers are usually located on the ceiling or near the top of a wall, while rectangular air registers tend to be at the bottom of a wall near the floor. Many air registers are also located on floors.

An air register deflector is a rectangular, plastic low-sided device. It's designed to fit over a register located on a floor near drapes or seating. Without a deflector, the airflow from straight slatted air registers will rise upwards into the drapes or seating. The deflector blocks the airflow from moving upward and instead redirects it under chairs and curtains through the opening created by the deflector's low sides. Deflectors for air registers are very inexpensive and can be purchased for less than $15 US Dollars (USD).

About Mechanics is dedicated to providing accurate and trustworthy information. We carefully select reputable sources and employ a rigorous fact-checking process to maintain the highest standards. To learn more about our commitment to accuracy, read our editorial process.
Discussion Comments
By OeKc05 — On Oct 31, 2011

No one has noticed yet, but I often manipulate the air duct register at work. I can’t concentrate when I’m either too hot or too cold, and since we’re not allowed to touch the thermostat, I sneak over to the air register and pull the lever around.

It has horizontal slats. If I am cold even with a sweater on because of the air conditioning, I will close the slats.

Sometimes, people get hot and see that the register is shut, and then I just have to deal with being cold after they open it. At least I get an hour or so in a comfortable environment before they notice.

By kylee07drg — On Oct 30, 2011

@shell4life - Fear of air registers may not be as uncommon as you may think. My daughter was terrified of our floor grill. She would not go near it, even to go get one of her toys.

She told me that she was afraid of falling into it. I told her that was impossible, because the little square gaps were tiny. She didn’t care.

I ended up getting a deflector to go over it to ease her anxiety. I was able to find a rust-colored deflector to match the grill. It looked like it belonged there.

We probably needed one, anyway. It pushed the air toward the center of the room rather than straight up, and since the grill was in a corner, this seemed to make the rest of the house feel warmer from the heat and cooler from the air conditioning.

By shell4life — On Oct 30, 2011

This may sound strange to most people, but I was terrified of air diffusers as a child! My parents took me to a big warehouse that had giant diffusers in the ceiling, and I was scared they would suck me up inside.

These diffusers were shaped like a target. They were made of several rings of metal with big, dark gaps in between. I had never seen any vent so huge in my life!

My parents told me that the place needed them because they were able to distribute enough air to cool or heat the giant building. Also, they were relatively quiet while directing the air.

It didn’t matter to me that they weren’t very loud. It wasn’t their sound that scared me. It was their massiveness and the black abyss that lurked within them! To this day, I still don’t like walking under them.

By wavy58 — On Oct 29, 2011

My office has a diffuser on the ceiling. It looks like a bunch of fan blades framed inside a circle and attached in the middle to a round piece of plastic.

The diffuser is gray to match the ceiling. It has so many stationary blades that the air gets sent out in all directions.

I love this, because I work right under the diffuser, and I would hate to have all that air blowing right on me. I’m cold-natured, and in the summertime, it’s way too cold inside the building anyway. I can’t imagine how I would feel if all that cold air were directed right at me!

Also, in the winter, the heat is spread out very well. Direct heat makes my sinuses and eyes dry out, but the diffuser keeps this from happening. I probably need to get one for my house to ease my suffering.

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