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Who knows what evil is hidden in the heart of the cast iron radiator? Given their cave-like internal structure, it can be anything—dust piles, pet and human hair, toenails, candy wrappers, or even large dry walls renovated a long time ago. All of these can lead to foul odors and reduce the efficiency of the home heating system.

Cast iron radiators often appear in older houses and apartment buildings. They usually use one of two designs-cylindrical and thin tubes. When distributing steam and/or hot water throughout the radiator, the internal heating mechanism is slightly different. However, externally, the working principles of these two types are basically the same. As the name suggests, they emit heat. But convection does work, and the air warms the room as it circulates naturally through the fins (the individual pillars that look like tall loaves of bread).

These radiators have no motors. But when it comes to understanding the accumulation of debris, Dan Holohan, author of "The Lost Art of Steam Heating" and founder of HeatingHelp.com, suggests to imagine how a hair dryer filter can become full of hair and dust. "Anything stuck between these fins will slow down convection," he said. This leads to a decrease in the efficiency of the radiator because the boiler must use more fuel to bring the room to the temperature you want. If you don't like the smell of your home, the radiator may be the culprit.

Given that radiators are difficult to clean, and the most serious dirt is usually hidden (unless you look for it), they usually go unnoticed for a few years. Wirecutter editor Jon Chase calls it "grotty rads," a phrase that no one wants to associate with their home.

Long brush: I use two different brushes, one of which is specially designed for radiators.

Vacuum cleaners or wet/dry vacuum cleaners with gaps and brush attachments: please note-dust will fly around during work. Having a vacuum cleaner on hand will help you clean anytime, anywhere and clean it when you are done. I started using our vacuum cleaner and chose Shark Navigator Liftaway NV352. I like its super long gap tool. But in the end my work requires the stronger suction power of a wet/dry vacuum cleaner.

Non-abrasive sponges: Use these sponges to wipe the outer surface of the radiator.

Dish towels: Any thin dish towels will do, but I prefer these and use them for all kinds of housework.

Larger old towel: Use an old towel to catch water droplets on the floor.

Mild detergent: You only need a few drops of mild detergent, such as seventh-generation detergent.

Two buckets: one is for soapy water, and the other is for washing.

Dust mask with filter: Use a breathing mask to protect your lungs from all the dust that is about to rise.

Big flat cardboard box: Place one of them behind the radiator and fix it with painter's tape to protect the wall from splashes.

Rubber gloves: If the inside of the cast iron radiator has been painted many times over the years, it will sometimes be very rough. You will need to use rubber gloves to protect your skin.

Old sheets or plastic sheets: If your radiator is too dusty, you may need to cover nearby furniture.

Headlights: Bright hands-free lights can help pinpoint problem areas deep in the radiator.

Safety glasses: Wear these glasses to protect your eyes from any accidental projectiles fired by the brush.

Toothbrush: If you don't have a grass brush on hand, old toothbrushes with soft bristles can reach tricky places (as long as they are not too deep in the radiator).

Pen, pencil or any other thin and narrow tool: Depending on the depth of the radiator, you can use one of them to pass the dish towel through the fins to pass through the gaps that are difficult to reach.

Pins or rulers, rubber bands, microfiber cloth: stick the cloth on any type of slender stick to make a DIY radiator brush.

There is no simple answer here. Whether you are performing deep cleaning or maintenance, the time required depends entirely on the size and style of the radiator. You need to consider the width and height, as well as the number of heat sinks on the model, the number of slits on each heat sink, and the number of units in your home.

I recently moved into a house built in 1934, and the radiator looks like it has not been cleaned in ten years. In my first attempt, it took me about 45 minutes to complete about 2.5 feet of an almost 5-foot-long radiator, including preparation.

This sounds extreme, but I'm working on a thin tube radiator, which usually has more cracks than a pillar radiator. Therefore, a 24-inch radiator means cleaning 12 heat sinks close together, each containing eight dust-filled slots. There are 96 hard-to-reach openings in total, and all openings need to be cleaned thoroughly. And I’m just getting started—my house has a total of 41 feet of radiators scattered throughout the room.

For the faint of heart or people with a bad back, dealing with this level of deep cleansing is not a chore. A column radiator with wider space between the fins and fewer gaps may complete the work faster. I believe that next year’s maintenance and cleaning will be easier. (Another 2-foot-long, not-so-dirty room in another room only took me about 30 minutes.)

Holohan recommends doing this once a year before turning on the radiator for the first time in each cold season. But retouching throughout the year will certainly not hurt.

If you have just bought or rented a new house and the radiator looks particularly dirty, I strongly recommend that you take care of this trivial matter before moving in, if possible, because of how much dust will be raised in the process.

Make sure your radiator is turned off and cooled completely. Use painter's tape to attach a flat cardboard box to the wall behind the radiator. This will protect your walls from false splashes of dirty water. If your radiator is extremely dusty, you may want to consider covering nearby furniture with plastic or sheets.

Check underneath the radiator (remove any large hidden objects) and vacuum the area. After vacuuming, place a towel under and around the radiator to catch falling debris and dripping water.

Wear a dust mask (and goggles and gloves if you are using them). Use the brush attachment on a vacuum cleaner or wet/dry vacuum cleaner to gently remove large dust piles, hair balls, and anything that is easy to reach.

For older radiators, it is particularly important to use a brush with soft bristles, because you want to minimize interference with the paint in case it is leaded (more on that later). Be sure to suck up all the debris that is easy to peel off with a brush.

The initial loose debris is a good test run to familiarize you with the needs of the radiator during the wet cleaning phase. If you have a thin tube model, you will begin to understand the specific angles needed to get into more difficult points, such as the innermost cracks. The light from the headlight can help pinpoint the clumps hidden deep in the groove.

If you don’t have a radiator brush, a microfiber towel tightly attached to the end of a wooden peg (or any type of thin and soft rod) with a rubber band is a good DIY hack, especially if your radiator is not too dirty Start.

I tried several radiator brushes. My favorite is Konex’s premium flexible medium-soft natural goat hair radiator, coil and ventilation brush because of its tapered bristles, flexible wire base and comfortable wooden handle. The brush also has a clever design technique: a transparent plastic tube covers the wire space between the bristles and the handle. This prevents the wire from bending during vigorous brushing (this is why I tried to quickly break the handle of another model).

Fill one bucket with warm water and a few drops of mild dish soap, then fill the second bucket with regular tap water. Use a soft sponge or dish towel to gently wipe the outside of the radiator with a small amount of soapy water, and wipe inward as much as possible. Then wipe again with normal water to help remove any soap left behind. Dry thoroughly with a dish towel.

After wiping all the spaces that can only be reached with your hands, soak the cloth in clean water, and then "floss" the inner part, pulling the cloth back and forth to remove any dirt stuck on it. Rinse the cloth and repeat (over and over again).

I did not use soapy water to clean the internal floss because it required a second round of flushing, and I didn't have time at all. Water alone can remove dirt well. But if I only deal with one or two radiators, I will clean them thoroughly with soap. This is your call, according to your needs and how much time you have.

If certain areas don’t look clean enough, you may find yourself getting more and more frustrated—especially when your radiator is painted lightly. But what looks like a stubborn sticky thing may just be stains or frayed paint. Repainting will help, and there are good step-by-step instructions on Bob Vila's website.

I find that wrapping the end of the dish towel around the eraser side of a capped pen or pencil helps to move the cloth in tricky areas until I can hold it properly from the other side of the narrow space to use dental floss.

A wet grass brush allows me to enter extremely narrow places—such as the space between the horizontal thin tube and the base—to get more stubborn, sticky dirt. An old toothbrush can also be used where it is easier to reach, but the longer handle of the grass brush allows me to get more inside.

Before turning on the heating, please try to dry the cleaned radiator thoroughly with a dry-cleaning dish towel as much as possible.

I think I did a good job of catching everything flying out of the radiator with a vacuum cleaner and a wet/dry vacuum cleaner. However, once the dust settles, after 24 hours, many nearby surfaces still need to be wiped clean with a microfiber cloth. This may not happen to everyone, but it needs attention.

Many old radiators are coated with lead paint, but Holohan said that smoke does not need to be worried because the radiator will not get hot, causing lead air pollution to become a problem. If your radiator is peeling off paint chips, test it with a household lead test kit before you start cleaning. If the test result is positive, please take extra precautions in accordance with the regulations of the Environmental Protection Agency.

We have seen people recommend using compressed air to help clean the radiator. Personally, I am not a fan of this idea, because forced eviction will cause dust to spread throughout the place, too wide and too fast to use a vacuum cleaner while you are away.

Finally, I think it’s important to note that “good enough” may be fine when cleaning the inside of an old radiator. This can be an extremely difficult, time-consuming, and frustrating task. It is very likely that after you spend a lot of time working, you will still see some areas that you simply cannot reach or have no energy to solve. Don’t slack off, and know that if you followed the steps above, you may have gotten out of the worst.

If you have some tips or tricks to clean the radiator more easily, please share in the comments.

Joshua Lyon is the editor of Wirecutter's emergency preparedness and home improvement topics. He has written and edited for numerous media including Country Living, Modern Farmer, New York Times, V and VMAN, Marie Claire, Jane and Food Network Magazine. He is also a writer and ghostwriter nominated for the Lambda Literary Award. Learn more on jklyon.com.

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