Dryer Lint Traps – Everything You Need to Know About Secondary and Dryer Duct Lint Traps
Every time you use your clothes dryer, you should clean the lint trap. A full lint trap can increase drying time, so it is important to make sure your washer and dryer are in optimal working condition for maximum efficiency and maximum safety.
Some dryer vent installations also have an external lint trap, which is also known as a secondary dryer lint trap or a 4″ In-Line Dryer Lint Trap, a dryer vent filter, or a lint catcher for dryer vents.
Quick answer: A dryer lint trap is a screen or mesh filter that catches lint before it travels down the vent. Every dryer has one built in near the door or drum. A secondary (or external) dryer lint trap is a separate device installed further along the duct — often called a dryer duct lint trap or lint collector for dryer exhaust systems — that catches whatever lint slips past the built-in screen.
What Is a Dryer Lint Trap?
This device acts as an in line lint filter in the dryer’s exhaust pipe. Its purpose is to provide additional protection for your dryer booster fan, and it also helps to prevent the dryer exhaust pipe from getting clogged with lint as quickly.
External lint traps are usually installed on clothes dryers that are located on an inside wall, or when the length of the dryer vent exceeds 20-30 feet. The shorter the overall length of the vent pipe and the fewer the number of elbows or turns in the pipe, the better. Under the International Residential and Mechanical Codes (IRC/IMC), a standard 4-inch dryer vent has a maximum “developed length” of 35 feet, reduced by 5 feet for every 90-degree elbow and 2.5 feet for every 45-degree elbow. In practice, many standard dryers move air effectively only up to about 25 feet without help — which is exactly why a booster fan paired with a secondary lint trap becomes necessary on longer runs. Longer vent lengths and turns all add restriction to the air flow, causing dryer lint to build up inside.
Built-In Lint Screen vs. Secondary Dryer Lint Trap: What’s the Difference?
| Built-in lint screen | Secondary (external) lint trap | |
| Location | Inside the dryer door or drum | Further down the exhaust vent, in-line |
| Also called | Lint filter, lint screen | Dryer duct lint trap, in-line lint trap, lint catcher for dryer |
| Cleaning frequency | Every load | Every 3–5 loads on average |
| Main job | First line of defense | Catches lint that escapes the built-in screen |
| Required by code? | Yes, standard on all dryers | Not always — recommended for long/turny vent runs, inside-wall installs, and multi-unit buildings |
How Can You Improve Your Dryer Lint Trap Setup?
A good way to do this is by having your dryer vent cleaning service by a professional on a regular basis. This is also where the secondary lint trap can help. Not everyone needs an external lint trap, and some homeowners who do have them often have questions about their use.
Regularly cleaning your dryer vent and lint trap:
- Cuts drying time and energy costs
- Reduces strain on the dryer motor and heating element
- Lowers the risk of a dryer duct fire
- Extends the life of both the dryer and the vent system
How Often Should You Clean a Secondary Dryer Lint Trap?
Check a secondary dryer lint trap every 3–5 loads — its clear door makes a visual check take seconds. The dryer’s built-in lint screen still needs cleaning before every load, without exception.
The lint trap has a clear door, so you can see through it. Check it before every load and you will quickly get an idea of how often yours needs to be cleaned… something like every 3-5 loads is average. That’s for the secondary lint trap. The one that came with your dryer still needs to be cleaned at the start of every load.
While not every load fills the trap, cleaning it after each load will help reduce energy use.
How Do You Open a Dryer Lint Trap Door?
That depends on the type of lint trap you have, however most work similarly. Here’s how to open the most common model, the LT-180:
1. Locate the knob on the plexiglass door.
2. Lift the knob up to release the door from its seated position.
3. Pull the door out from the bottom.
4. Empty the lint and wipe down the screen if needed.
5. Reverse the steps to reseat it: slide the door back in at the bottom, then press the knob down to lock it in place.
It’s very easy once you try it a few times.
Where Is Your LT-180 Lint Trap Installed — On the Wall or Behind It?
Your LT180 lint trap can be installed either on the wall (highly visible) or inside the drywall. If this is the case, then you would only see a plexiglass door with two small folds of metal on either side. This could be on the ceiling near your dryer or on the wall.
The photo above shows an extremely dirty lint trap. The condo owner had recently moved in and did not realize they even had one of these.
Buying a Dryer Lint Trap: What to Look For (Home Depot & Big-Box Options vs. Commercial-Grade)
The LT-180 is the best we have found so far. It is made in Canada, is constructed of thick metal and is of commercial quality. This lint trap is a permanent model.
Over time (years) the door may crack or the screen may become damaged or frayed. It will help to know that the door and screen can be replaced seperately, and those cost about $20. If you have a broken door on your model LT180 lint trap, feel free to call us and we can send you a new one.
Some Do-it-yourselfers prefer to buy a dryer lint trap from Home Depot, but they also offer several other models as well. There are cheaper quality plastic ones, but it is recommended that you purchase the more durable and slightly more expensive model LT180. The metal one is much more sturdy and will be problem-free.
| Standard plastic lint trap | LT-180 metal lint trap | |
| Material | Plastic housing | Thick metal, commercial quality, made in Canada |
| Typical lifespan | Shorter — prone to cracking | Long-term, built for repeated use |
| Repairable? | Often replace the whole unit | Door and screen replaceable separately (~$20 each) |
| Best for | Occasional/light residential use | High-frequency use, longer vents, condos/multi-unit buildings |
Risk Of Dryer Duct Fires
Dryer duct fires are a very real and serious threat. According to the National Fire Protection Association (NFPA), U.S. fire departments respond to roughly 14,000–16,000 home structure fires involving clothes dryers and washing machines each year, causing dozens of deaths, hundreds of injuries, and well over $200 million in property damage annually. Failure to clean the dryer and its vent system is consistently cited as the single leading contributing factor, involved in roughly a third of these fires.
Any home or business that operates a clothes dryer needs to take proper precautions, including considering the use of a secondary lint trap for electric dryer, to reduce this risk as much as possible, regardless if your machine is gas or electric.
Dryer lint is very flammable and can accumulate inside a vent pipe fairly quickly. It is recommended that dryer vent cleaning service be used once per year.
Do Condos and Multi-Unit Buildings Need a Secondary Lint Trap?
Condos and apartment buildings often route several units’ dryer vents into one shared exhaust stack, which tends to be longer and turnier than a single-family home’s vent run. That combination — length, shared use, and more elbows — is exactly the scenario where building codes and HOA guidelines are most likely to call for a secondary lint trap and booster fan. If you manage or live in a multi-unit building and aren’t sure what’s installed behind your dryer, it’s worth having it inspected rather than assuming.
More Info About Secondary Lint Traps
Dryer Lint Trap Maintenance Checklist
– Clean the built-in lint screen before every load
– Check a secondary/inline lint trap every 3–5 loads
– Schedule professional dryer vent cleaning at least once a year
– Watch for warning signs: longer drying times, a hot dryer exterior, or a burning smell
– Keep the vent run as short and straight as possible — every elbow adds resistance
– Replace a cracked door or frayed screen promptly rather than running the dryer without it
Below are some useful links that we’ve found regarding the safe operation of your clothes dryer, and how to help prevent a dryer fire in your home or business.
Taking care of your clothes dryer is important for home fire safety.
Clothes Dryer Maintenance and Fire Prevention Tips
Cleaning the Dryer Exhaust Fan and Ducts in Your Condo
If it’s been a while since your vent system was last inspected, schedule a dryer vent cleaning with our team — we’ll check both your built-in lint screen and any secondary lint trap as part of the visit.
Frequently Asked Questions
What is a secondary dryer lint trap?
A secondary (or external) dryer lint trap is an in-line filter installed in the exhaust duct itself, separate from the dryer's built-in screen. It's also called a dryer duct lint trap or 4″ in-line lint trap.
How often should I clean a secondary dryer lint trap?
Every 3–5 loads on average, checked through its clear door. The dryer's built-in lint screen still needs cleaning before every load.
How do I open an LT-180 lint trap door?
Lift the knob to release the door, then pull it out from the bottom. Reverse the steps to close it.
Does every dryer need a secondary lint trap?
No. They're most useful when the dryer sits on an inside wall, the vent run exceeds 20–30 feet, there are several elbows, or the building is a condo/multi-unit with a shared vent stack.
Can a clogged lint trap cause a dryer fire?
Yes. Lint is highly flammable, and a blocked trap restricts airflow, causing heat to build up. Failure to clean is the NFPA's leading contributing factor in home clothes dryer fires.
How much does it cost to replace a lint trap door or screen?
On the LT-180, the door and screen can be replaced separately at roughly $20 each.
Also Read: Dryer Duct Fires and How to Help Prevent Them
Also Read: 5 Important Dryer Duct Safety Tips
