We are all aware of the fire risks caused by cooking, smoking or the use of candles in the home. Many consumers are not aware of the fire risk which can be caused by household appliances. Tumble dryers are heat-producing appliances, which can cause fire for several reasons, just two being manufacturer defects and the lack of care on the part of the user. By highlighting the potential threats faced by tumble dryer fires, it is hoped that potential tumble dryer fires can be prevented.
As someone who attends fire investigations on a frequent basis, I understand all too well the ignition potential faced by tumble dryers and the damage caused. In an efficient tumble dryer, the inlet air temperatures may exceed 350°C in the heater box but drop quickly to operating ranges between 50°C and 80°C within the drum. Tumble dryers have several safeguards, such as high-limited thermostats to ensure that the laundry load is not overheated, but if the appliance is exposed to multiple failures or poor installation/maintenance practices, there exists the potential to exceed these normal ranges, and a fire can ensue.
However, many fires involving tumble dryers occur where these engineering safeguards operate properly, and the fire appears to have been caused by ignition of the load in the drum. See image below for a fire occurring within the drum space.
Self heating Events
Laundry contaminated with drying oils, cooking oils and massage oils have been revealed to lead to self-heating of washing loads. Self-ignition (spontaneous ignition) is defined as the delayed ignition of a pile of solid combustible materials due to internal heat generating processes. Self-heating is caused if the combustible load generates more heat than it loses to the environment, the temperature may rise high enough to initiate smouldering combustion that can lead to fire.
Linseed oil is one of the most widely known oils that exhibits self-heating behaviour. Many fires are caused when oils are cleaned up in rags and placed into the tumble dryer.
Probably the most well-known cause of fire from tumble dryers is the build-up of lint from within the tumble dryer casing. This accumulation of lint can get forced through the air distribution system, if it reaches the heater system, it can ignite. For condenser tumble dryers, the condensing chamber needs to be cleared out and free from obstruction.
Some 5.3 million tumble dryers under the Hotpoint, Creda, and Indesit brands, all of whom are manufactured by Whirlpool, have been recalled due to a potential fire risk. Whirlpool has estimated that between 300,000 and 500,000 fault affected tumble dryers could still be in consumers’ homes today. This is a frightening thought and something you should think about.
A major recall issue has been reported to include poorly designed printed circuit boards. This is possibly as a result of cost cutting and cheaper materials used. PCB’s are not built to a high enough standard to effectively carry the high currents associated with heater elements. Such faults can result in electrical failures originating at the PCB with fire spread at that location.
Problems have been reported with door switch assemblies on some brands. This can be caused when the user opens the door before the cycle finishes. Other recall faults include compactor failure, lack of ventilation and lint build-up in areas where it shouldn’t be.
So how can we prevent such fires from occurring in our homes
Many fire have occurred when the user leaves the machine unattended during the drying cycle or after the machine has finished. We can all be guilty of adding a load of laundry to a drying cycle, sit down and forget about the clothes after the cycle has finished. Clothing should not be left in the tumble dryer after the drying process is finished but should be unloaded immediately. This will prevent heat build-up and allow the clothing to aerate. Laundry should also not be over-dried in the tumble dryer. Not only are you wasting electricity, you are increasing the chances of the load igniting.
As we have seen, tumble dryers are a credible fire ignition risk. I would urge people not to leave tumble dryers turned on unattended when they leave the house. Never add a load to the tumble dryer before bed – if you do, make sure you have an operational smoke alarm. After every use, clean the filter on your tumble dryer and minimise the chances of ignition occurring. For condenser tumble dryers, clean the condenser chamber.
Avoid placing clothes covered in oils into the dryer without first washing thoroughly as they are known to pose a risk of spontaneous ignition when soaked onto rags. If any of you are worried that your tumble dryer may be affected, check out https://www.uk-afi.org/product-recall and check your tumble dryer model number against the recall database.