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Measuring temperature at the hot air inlet of a Maytag LP gas clothes dryer (C) Daniel FriedmanDryer & Dryer Vent Temperatures

Safe & Unsafe Temperatures in the Clothes Dryer & its Vent

Clothes dryer temperatures and fire risk.

This article on clothes dryer temperatures gives the normal operating temperature at different points inside the clothes dryer appliance and its venting system.

We include also unsafe temperatures that might be reached during various dryer faults or conditions and temperatures that could cause a dryer fire.

Page top image: the author [DF] measuring the approximate surface temperature of the hot air inlet of a Maytag LP gas fueled residential clothes dryer. With the dryer heat set to high and the gas burner on and stabilized the temperature was approximately 140 °F (60 °C).

This article series describes good practices for clothes dryer vent installation, lint traps, wall vents, filters, and screens.

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- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

Clothes Dryer & Dryer Vent Temperatures & Fire Hazards

Dryer vent installation, sloppy © D Friedman at InspectApedia.com This discussion gives the various temperatures found inside of clothes dryers, in and at the clothes dryer tumbler or drum, heater, and in the dryer exhaust vent during both normal safe operation and during unsafe conditions that risk a dryer fire or building fire.

We include a table of the temperatures that occur inside of clothes dryers at different places in the equipment and in its venting system and we describe unsafe dryer operating temperatures.

Photo: a long horizontal clothes dryer vent like that shown may be prone lint clogging and could risk a building fire.

The two principal contribution made by clothes dryers to building fires are

  1. High operating temperature inside the dryer
  2. Lint accumulation on the dryer blower or elsewhere in the dryer's air path - (Hall 2005), slowing air movement, blocking heat exhaust, causing abnormally-high & unsafe temperatures in the dryer or its venting system.

75-80% of U.S. clothes dryers are electric, 20-25% are fueled by natural gas or LP gas (Bonaccorso 2012), (Energy Star, 2011). The number of clothes dryer fires is distributed approximately in these same percentages. - (CPSC Residential Fire Loss Estimates (Miller, 2012))

The US CPSC estimated an annual rate of 6100 clothes dryer fires, 20 deaths, 190 injuries & property loss of about $80 million between 2008-2010. - CPSC Residential Fire Loss Estimates (Miller, 2012)

The NFPA estimated an annual rate of 16,800 fires, 51 deaths, 380 injuries & property loss of about $236 million - NFPA Annual Fire Loss Report, Home Fires Involving Clothes Dryers and Washing Machines (2010).

High clothes dryer operating temperatures may also contribute to failure of the electric motor operating the tumbler-drum.

Other dryer failures that can lead to high temperatures include the humidity sensor, temperature control system, blower motor/fan, timer control, shutoff control switches.

Table of Clothes Dryer Temperatures
Clothes Dryer Location / Condition Normal Clothes Dryer Temperature Abnormal / Unsafe Clothes Dryer Temperature Comments / Source
Air inlet to the clothes dryer & into dryer heating element

18 °C (64 °F) to 24 °C (75 °F)

 

   Building indoor ambient temperature, conditioned space, comfortable temperatures for sedentary adults3
Air temperature at an electric clothes dryer heater element 120-200°C (250-400 °F)   Varies by dryer heat source such as electric vs gas. (Marks, 2012) cited in (Bonaccorso 2012)1
Air temperature entering the clothes dryer tumbler / drum 80 °C (175 °F)   (Marks, 2012) cited in (Bonaccorso 2012)
Air temperature inside the clothes dryer drum / tumbler 50-57 °C (125-135 °F) > 200 °C (392 °F) Some sources claim 65 °C (150 °F) - informal search 2017/07/17
Air temperatures in the clothes dryer exhaust vent at the dryer 50-57 °C (125-135 °F) > 200 °C (392 °F) (Marks, 2012) cited in (Bonaccorso 2012) 1
Estimated clothes dryer exhaust vent surface temperature at interior surface of exterior wall 45-55 °C (113-130 °F) > 200 °C (392 °F) Author's IR temperature measurements 1,2
Estimated clothes dryer exhaust vent interior surface temperature at exterior wall vent outlet 37-62°C (100-145 °F) > 200 °C (392 °F)

Author's IR temperature measurements 1,2

Dryer vents that pass through hot roof cavities may reach the elevated temperature at the high end of this range.
Pyrolysis temperature range   90 - 150 °C (200-300 °F) PYROLYSIS EXPLAINED (Kim 1994) in (Bonaccorso 2012) warns of pyrolysis hazards at clothes dryers.
Maximum safe temperature inside a clothes dryer <= 200 °C (392 °F) > 200 °C (392 °F) 232°C (450 °F) is the combustion point of paper - in a clothes dryer could initiate a lint or other fire "... no location inside the cabinet can achieve this temperature throughout the seven hours of performance testing" - (Bonaccorso 2012).

Notes to the table above

Watch out: potential fire hazards associated with clothes dryers are discussed

at CLOTHES DRYER SAFETY CHECKLIST

Watch out: clearance distances between the wall exhaust point and other equipment are explained

at CLOTHES DRYER VENT CLEARANCES & TERMINATION

1. Scholarly and accurate clothes dryer temperature measurements using direct-contact temperature sensing devices were performed by Bonaccorso (2012) cited

at CLOTHES DRYER FIRE RESEARCH.

2. Poughkeepsie NY July 2017- D Friedman (2017) Field measurements of clothes dryer and dryer vent actual on-site measurements conducted by the author [DF] are described

at CLOTHES DRYER TEMPERATURE MEASUREMENTS

3. Höppe (1999), Wikipedia (2017)

 

Gas Clothes Dryer Temperature Measurements

In July 2017, using an Exergen infrared thermometer, I [DF] measured surface temperatures at key locations inside of a gas fueled clothes dryer where I was surprised to find vent temperatures at the building exterior wall were higher than temperatures measured in and close to the clothes dryer itself.

Details are reported at are described

at CLOTHES DRYER TEMPERATURE MEASUREMENTS

Clothes Dryer Exhaust Vent Installation, Dryer Temperatures, Dryer Fires Research

Citations mentioned in this article as well as additional clothes dryer operation, temperature, fire hazard research material has moved

to CLOTHES DRYER FIRE RESEARCH


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Citations & References

In addition to any citations in the article above, a full list is available on request.

  • [7] "Healthy Indoor Air for America's Homes, Indoor Air Hazards Every Homeowner Should Know About - room by room assessment", U.S. Government Publications, web search, 11/30/2011, original source: http://publications.usa.gov/epublications/indoorair-hazards/assessment.htm More about this information source, quoting the US Government website:

    ... Federal Citizen Information Center (FCIC) has been a trusted one-stop source for answers to questions about consumer problems and government services. FCIC, part of the General Services Administration's Office of Citizen Services and Innovative Technologies, has traditionally provided publications to consumers via the publications distribution center in Pueblo, Colorado.

    The Pueblo.GSA.gov website was where consumers could go to find information and order publications on a variety of topics from the federal government.
    Publications.USA.gov replaces the former Pueblo.GSA.gov.
  • [8] "The Facts About Clothes Dryer Exhaust Systems", John Cranor, the ASHI Reporter, April 2005,American Society of Home Inspectors,® Inc., 932 Lee Street, Suite 101, Des Plaines, Illinois, 60016, Tel: 847-759-2820, website: ashi.org, original source: ashireporter.org/articles/articles.aspx?id=161
  • [9] Tjernlund Residential Capacity Dryer Duct Booster®, "Dryer Duct Booster Fan Model LB1, Installation Instructions" [PDF], Tjernlund Products, 1601 9th Street White Bear Lake, MN 55110-6794 , (800) 255-4208, web search 01/06/2012, original source: tjernlund.com/dryer_booster.htm Quoting:

    The Dryer Duct Booster®, Model LB1, has been specifically designed to boost residential capacity clothes dryer duct exhaust velocities where dryer duct runs exceed 25 equivalent feet. Proper exhaust velocities will reduce drying times, save energy and prevent lint buildup in the dryer duct.

    The LB1 is controlled by an electronic Pressure Response Control (PRC) for automatic operation.

    The LB1 utilizes galvanized steel construction, a reverse inclined, particulate handling impeller that is guaranteed not to clog with lint and an externally mounted PSC motor for trouble-free operation.
  • In addition to citations & references found in this article, see the research citations given at the end of the related articles found at our suggested

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