Reuben's Home Inspection Blog


Clothes dryers, lint, and fires

According to Underwriters Laboratories, clothes dryers are responsible for approximately 15,000 home fires each year.    It's not hard to believe.  Improperly installed and improperly maintained clothes dryer ducts are one of the most common issues that home inspectors find, but it's not that difficult to keep your clothes dryer safe.  Today I'll discuss dryer duct installations and maintenance.


In Minnesota, the installation requirements for clothes dryer ducts can be found in Section 504 of the Minnesota Mechanical Code.   I won't go over all of the requirements, but I will mention a few of the items that most people have questions about.

Dryer duct length - the maximum allowable length for a clothes dryer duct is 25'.  Each 90 degree turn in the duct is worth 5', and each 45 degree turn is worth 2.5 feet.  For a typical basement in Minneapolis or Saint Paul, the clothes dryer has a 90 degree turn in the duct right behind the dryer, then another 90 degree turn at the ceiling.  Assuming it's a 7' ceiling, this leaves 8' of run before the dryer duct needs to terminate at the exterior, according to these requirements.

While many clothes dryers have a longer run than this, it's not always a problem.   There's an exception to the rule which says "where the make and model of the clothes dryer to be installed is known and the manufacturer's installation instructions for such dryer are provided to the code official, the maximum length of the exhaust duct, including any transition duct, shall be permitted to be in accordance with the dryer manufacturer's installation instructions.".  

In other words, if the dryer manufacturer allows a longer duct, no problem.

I've read a lot of dryer installation manuals, and in every case the dryer manufacturer allowed for a much longer run than what's allowed by code; for instance, a 29" Maytag clothes dryer allows for a 100' duct when two elbows are used.

I once inspected a condo conversion building in Saint Louis Park where the contractor had attached a placard to the location where the dryer would go, warning that the maximum length of the drier (sic) vent was limited to 30' with three elbows.

Dryer vent placard

Dryer duct construction - dryer ducts need to vent to the exterior, be made from metal, be at least 4" in diameter, and have a smooth interior.  The entire duct needs to be supported and secured, and no screws are allowed on the joints because they could accumulate lint.  Flexible materials, such as foil, plastic, and semi-rigid metal aren't allowed.  Those are all common materials used for a dryer transition duct - the material that can be used to get from the dryer to the duct.

Dryer transition duct

The terminal for the dryer needs to have a backdraft damper, and no screens are allowed at the dryer exhaust.  When screens are installed, they get clogged with lint.  This reduces the performance of the dryer and creates a potential fire hazard.

Clogged dryer duct

I've heard concerns about pests getting in to the clothes dryer duct if a screen isn't installed, but if the backdraft damper at the exterior is kept clean, this shouldn't be an issue.

Transition Ducts are a big enough topic to deserve their own post.  I'll write about these next week.

Clothes Dryer Maintenance

Clothes dryer maintenance is actually quite simple: keep it clean.  Dryer lint is flammable, and the more that accumulates in the dryer and the duct, the greater the risk.  The most obvious and routine part of this is keeping the lint screen clean - it should be cleaned after every load.

Periodically check the damper at the exterior to make sure it's clean; when lint accumulates at the damper it will eventually cause the damper to stay open.

Dirty dryer terminal

If you're unfortunate enough to have a dryer that exhausts through the roof... I'm sorry to hear it.  Someone needs to get up there on a regular basis to clean the damper.

If you have a dryer duct that passes through a concealed or infrequently visited space, such as an attic or crawl space, you should check on it periodically to make sure that everything is still properly connected.  A disconnected clothes dryer duct will exhaust a ridiculous amount of lint and moisture in to the home.

Disconnected dryer duct in crawl space

Take a peek behind your dryer with a flashlight periodically - it's quite common for the dryer to come disconnected from the duct, which makes a big mess of flammable lint behind the dryer.  The dryer duct itself needs to be cleaned periodically as well.  You can find instructions for cleaning your own dryer duct here -  This sounds like a good project for the next rainy weekend.

I'll have plenty more to discuss next week on the topic of clothes dryer transition ducts.

Reuben Saltzman, Structure Tech Home Inspections


Comment balloon 44 commentsReuben Saltzman • August 07 2012 03:13AM


I will bookmark this post and check out my dryer at home. Thanks for the post.

Posted by Gita Bantwal, REALTOR,ABR,CRS,SRES,GRI - Bucks County & Philadel (RE/MAX Centre Realtors) almost 7 years ago
Very important subject for homeowners, right up there with smoke detectors and CO alarms, thanks.
Posted by David Popoff, Realtor®,SRS, Green ~ Fairfield County, Ct (DMK Real Estate ) almost 7 years ago

Gita - thanks!

David - absolutely.  This is just basic stuff that you need to be aware of if you own a clothes dryer.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 7 years ago

I am removing the flexible ducting for my clients' rental properties when the "run" to the exterior is too long.....the cost is minimal and it provides me peace of mind

Posted by Wallace S. Gibson, CPM, LandlordWhisperer (Gibson Management Group, Ltd.) almost 7 years ago

OK Reuben...I will check my dryer line. Really...that many fires every year...great post.

Posted by Jeffrey DiMuria 321.223.6253 Waves Realty, Florida Space Coast Homes (Waves Realty) almost 7 years ago

Good one again Reubs.  I have had a couple of these and dryers are probably the most dangerous appliance in the house.  And so little attention is paid to it.

Posted by Jay Markanich, Home Inspector - servicing all Northern Virginia (Jay Markanich Real Estate Inspections, LLC) almost 7 years ago

Great information here.  Thanks so much for sharing.  I am heading to my basement to make sure my dryer is properly vented and safe!  

Posted by Amanda Christiansen, Christiansen Group Realty (Christiansen Group Realty (260)704-0843) almost 7 years ago

Good info.. i did not know this about the length of the vent

Posted by Janis Borgueta, LIC RE Salesperson (Key Properties of the Hudson Valley ) almost 7 years ago

Reuben, good information! I put a new one in a year ago. I will check it. Thanks.

Posted by Michael Setunsky, Your Commercial Real Estate Link to Northern VA almost 7 years ago

This was right across the street from my house. Quite a mess, took 9 months of repairs until they moved back in. $60,000 damage. 

Posted by Scott Seaton Jr. Bourbonnais Kankakee IL Home Inspector, The Home Inspector With a Heart! (SLS Home Inspections-Bradley Bourbonnais Kankakee Manteno) almost 7 years ago

Here's a thought to your worthy post...whoever designs a little zapper that attaches to the duct vent that vaporizes the link LINT into nothingness is the next billionaire

Posted by Richie Alan Naggar, agent & author (people first...then business Ran Right Realty ) almost 7 years ago

We use dryer lint in Scouts as a fire starter, if you ever used a flint and steel to spark a fire, you will understand how serious the fire hazard is!

Posted by Robert Rauf (HomeBridge Financial Services (NJ)) almost 7 years ago

Reuben, good information that most of us have missed the first time around (when we did not read the owner's manual ;-).

Posted by Chris Smith, South Simcoe, Caledon, King, Orangeville Real Esta (Re/Max Chay Realty Inc., Brokerage) almost 7 years ago

Ever since I first heard about the possibility of fire, I no longer put the dryer on and leave my home.  I was told by an extermnator to put a screen over my dryer vent outside because I did have a mouse in my dryer.  Thankfully, my husband never got around to it as now that I read your post, I would be worried about it.   Thanks for the great information.  

Posted by Susan Mangigian, Chester & Delaware County Homes, Delaware and Ches (RE/MAX Preferred, West Chester, PA, RS152252A) almost 7 years ago

The issue of the lint is serious and is a potential problem for a lot of homes.

Posted by Tim Lorenz, 949 874-2247 (TIM LORENZ - Elite Home Sales Team) almost 7 years ago

Something to think about for rental properties too. Surely most tenants don't keep the ducts and lint screen clean. 

Posted by Athina Boukas, Certified Residential Specialist (CRS) (Virginia Capital Realty) almost 7 years ago

Very sad that people are so stupid as to think they can plug in an appliance and thats it.  I never ever leave my home with an appliance running and my things are maintained to perfection.

Posted by Chris and Dick Dovorany, Broker/Associate at Premiere Plus Realty ( Homes for Sale in Naples, Bonita Springs and Estero, Florida) almost 7 years ago

Checking our dryer today!

Posted by John McCormack, CRS, Honesty, Integrity, Results, Experienced. HIRE Me! (Albuquerque Homes Realty) almost 7 years ago

This is one to print and bring home to Bud to check out! Thanks for sharing~

Posted by Bud & Beth McKinney, Cary/Raleigh/Apex NC - The Team That Cares, RE/MAX United (RE/MAX UNITED) almost 7 years ago

Excellent information that all of us shouldn't only know, but put into practice when it comes to maintaining our dryer.

Posted by David Burrows, No Pressure, Just Seriously Devoted to Real Estate (Classic Realty) almost 7 years ago

I check my dryer frequently, especially after a partiularly 'fuzzy' load such as blankets. In winter I use the lint for the fireplace and as noted earlier, it does burn fast without much effort to get it going.   I don't make the wax firestarters my little scout friends do, but tuck it down in a tube from toilet paper or paper towels.  Don't just throw it in the fireplace. It can also be added to paper mache.

Aside from fire, a dryer operates much more efficiently with a clean filter.  That is good for the utility bill and the lifespan of parts.


Posted by JudyAnn Lorenz, Virtual Marketing Consultant (Bar JD Communications) almost 7 years ago

You're preaching to the choir here. I see these messes all the time and blogged on them before. My favorite photo is the one on fire. Firecode basically doesen't want transition ducts at all.

Posted by Robert Butler, Montreal Home Inspector | Aspect Inspection (Aspect Inspection) almost 7 years ago

More people should pay attention to this.  You don't know how many times I've dealt with clients who don't pay a bit of attention to a lint trap until it becomes a problem.  And you're right about the damper on the roof.  Been there and it ain't easy.

Posted by Morris Massre, Real Estate Instructor Broward County Florida almost 7 years ago

Hi Reuben, you would think that since there is the potential for real tragedy from trapped lint, that it would be easier to clenn inside the duct and not have to hire someone else with special equipment to do it. That is how it is here in my neighborhood where the ducts are very long. Great post!

Posted by Sandy Acevedo, RE/MAX Masters, Inland Empire Homes for Sale (951-290-8588) almost 7 years ago

Thank you for drawing awareness to this potential disaster.  I know because I had a dryer fire.  Thank heavens I was home and caught it right away.  I learned you should routinely wash your lint trap with soap and water to prevent build-up.  I'm going to pull mine out right now and give it a good scrubbing!

Posted by Barb Merrill, GRI, Associate Broker (Cactus Mountain Properties, LLC) almost 7 years ago

Wow, what a "beautiful" photos! thank you for the post. During home inspections I've seen it all :)

Posted by Tatyana Makarov, Your Greater Hartford Area Realtor (Coldwell Banker Residential Brokerage) almost 7 years ago

I've seen some funky ones out there. People need to stay up on this.

Posted by Robert L. Brown, Grand Rapids Real Estate Bellabay Realty, West Mic ( almost 7 years ago

And I thought most of these installation directions were just suggestions.

Posted by William Feela, Realtor, Whispering Pines Realty 651-674-5999 No. (WHISPERING PINES REALTY) almost 7 years ago

Reuben, the photos are so graphic - the one with the grid reminds me of the dust that gets on my blow dryer and ruins them. Ours vents through the roof - guess Frank has a task to do :)


Posted by Sharon Alters, Realtor - Homes for Sale Fleming Island FL (Coldwell Banker Vanguard Realty - 904-673-2308) almost 7 years ago

Thanks for the reminder of this important/dangerous issue. We had a dryer vent fire once, but luckily we were home and once I smelled smoke and turned the dryer off, the fire went out on its own. It would have been a very different story if I hadn't been right there.


Posted by Mel Ahrens, MBA, Kelly Right Real Estate, Customized Choices for your Real Estate Needs (Kelly Right Real Estate) almost 7 years ago

I think the duct should be insulated when it passes through cold spaces. The hot damp lint is just looking for a cold pipe to stick to.

Posted by Rob Ernst, Reno, NV-775-410-4286 Inspector & Energy Auditor (Certified Structure Inspector) almost 7 years ago

Having seen the effects of this first hand I have learned what you are teaching. One of the most dangerous situations in a home.

Posted by Charles Stallions Real Estate Services, Buyers Agent 800-309-3414 Pace and Gulf Breeze,Fl. (Charles Stallions Real Estate Services Inc) almost 7 years ago

Reuben, your photos are graphic!  I am fortunate that my vent line is about 3 feet.  As a Realtor I have seen everything!

Posted by Sharon Parisi, Dallas Homes (United Real Estate Dallas ) almost 7 years ago

I was surprised to learn the same about your blog---  I loved it.I am a big fan of your blog.i am so excited by read of your blog's content.really great post.Thanks for sharing.

<a href="">Fire Extinguisher Maintenance</a>

Posted by Fire Extinguisher Maintenance almost 7 years ago

Wallace - great idea.  You'll improve the performance of the dryers as well.

Jeffrey - crazy, huh?

Jay - no doubt.  I had a family member complain about their clothes dryer taking forever to dry the clothes... and I found a gigantic chunk of lint completely blocking the dryer exhaust at the exterior.  Bad times.

Jared - thanks.

Janis - check your manual though.  Allowable lengths vary.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 7 years ago

Scott S - wow, and right next to your house?  Scary stuff.  Did you ever find out what caused the dryer duct fire?

Richie - just like the bug zapper?  That would be cool.

Robert - I bet!  It's even better than paper. 

Chris - say it ain't so ;)

Susan - I've seen a ton of houses with screens over the dryer ducts that were installed by exterminators.  Bad news.  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 7 years ago

Athina - definitely.  I've been in some rental properties where the landlords have put up big notices by the dryers reminding the occupants to clean the lint screens after every load.

Chris and Dick - it sounds like you shouldn't have much to worry about :)

John- good stuff.

Beth - I'll have a follow up to this on Tuesday as well.

David - exactly.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 7 years ago

JudyAnn- that's a great idea!  I might have to start saving my dryer lint and toilet rolls for that purpose.

Robert - I've noticed.  Even though the foil transition ducts are UL Listed, many AHJs in my area won't allow them.

Morris - I especially wonder what people where thinking when the exhaust terminals are located on steep two-story roofs.  I know plenty of home inspectors who don't even get on those.

Sandy - all the more reason to make sure it's maintained properly.

Barb - I've never heard of the soap and water thing, but it couldn't hurt.  My little trick is whenever I have my wet/dry vac out and I'm using it near the laundry room, I vacuum down my dryer lint screen.  Seems to do a pretty good job.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 7 years ago

Tatyana - I'll have some even better photos next week :)

Robert - correct.  This is important stuff.

William - ha!  :)

Sharon - I know exactly what you mean with the hair dryer.  I've cleaned my wife's...

Gretchen- good catch!  The video Scott posted in comment #10 might be a good example of what could have been.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 7 years ago

Rob - definitely.  If it's not insulated, you'll get plenty of condensation inside the duct.  Here in MN, the last 3' of the duct also needs to be insulated before it gets to an unconditioned space.

Joyce - and clothes dryers seem so innocuous...

Sharon - that's a nice length :).  Short and sweet.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 7 years ago

I've found disconnected ducts in attics and crawl spaces. It does make the place smell good :)

Posted by James Quarello, Connecticut Home Inspector (JRV Home Inspection Services, LLC) almost 7 years ago

Such a good post and lots to take heed to. We never think of these things till perhaps it is too late

Posted by Charles Stallions Real Estate Services, Buyers Agent 800-309-3414 Pace and Gulf Breeze,Fl. (Charles Stallions Real Estate Services Inc) almost 7 years ago

Reuben, the dryer fire started with a stuffed lint trap, in the dryer, went thru the vent up the wall and into the daughter's bedroom, then thru the walls into the attic. First responder showed up with a fire extinguisher. They were home and got out safely. 

Posted by Scott Seaton Jr. Bourbonnais Kankakee IL Home Inspector, The Home Inspector With a Heart! (SLS Home Inspections-Bradley Bourbonnais Kankakee Manteno) almost 7 years ago

Reuben, Good stuff as always. Love the lint forest pictures. I had one just a couple of weeks ago.

Posted by Donald Hester, NCW Home Inspections, LLC (NCW Home Inspections, LLC) over 6 years ago