Phoenix Journal · Ductwork
A tumble dryer that suddenly needs two cycles where one used to do the job is rarely worn out - it is usually starved of airflow. The cause almost always sits inside the ducting, not the drum.
The short answer
If your tumble dryer has quietly started taking longer to finish a load, the drum and heating element are usually working perfectly well - they simply cannot shift the moist air fast enough. Nine times out of ten the culprit is a duct that has slowly filled with lint, and the fix is restoring airflow rather than replacing the machine.
A dryer works by heating air, passing it through your washing to pick up moisture, then pushing that warm, damp air out through a vent or duct to the outside. When that exit route narrows, every part of the cycle drags. The good news is that this is a maintenance problem, not a fault - and the same principles that keep a commercial kitchen extract system breathing apply here too.
Longer drying times are the single most common sign of a restricted duct, but they rarely arrive alone. Run through the lists below - if you recognise more than one or two points, airflow is almost certainly the issue.
In a home, a lint-blocked dryer is an annoyance and a slow drain on your electricity - the sensible answer is to empty the filter after every single cycle, clear the vent hood regularly, and keep the external ducting as short and as straight as the room allows. Building guidance is blunt on this last point: the usable length of a dryer duct is cut back sharply for every bend it contains, because each turn creates turbulence that slows the air and gives lint somewhere to settle. A run that looks generous on paper can behave like a far shorter, choked one once two right-angle bends are in the way.
Step up to a hotel laundry, a care home, a launderette or any building running dryers hard all day, and the picture changes completely. Volume is higher, ducting is longer and often hidden above ceilings, and lint accumulates far faster than anyone tends to notice. Here the slow-drying symptom is the least of it. Fire and Rescue Services attended 23,008 accidental dwelling fires in England in the year to March 2024, and more than half - some 12,492 - involved domestic appliances, with white goods such as tumble dryers a recurring cause. In Wales, dryers alone have accounted for well over half of all white-goods fires in recent years. Lint building up near a heat source is the thread running through the majority of them.
That is why commercial laundry ducting is treated as a life-safety system, not a convenience. Under the Regulatory Reform (Fire Safety) Order 2005 - and the Fire (Scotland) Act 2005 north of the border - the Responsible Person for a premises must identify and control fire risks and keep fire precautions maintained. A lint-laden dryer duct is exactly the kind of risk that order expects you to manage, and most commercial property insurers now ask for evidence of regular cleaning as a straightforward condition of cover. For busy operations, a professional clean of the dryer ducting every six to twelve months is the widely accepted benchmark, with heavier users sitting at the shorter end of that range.
There is a strong commercial case beyond compliance, too. A duct cleaned back to its full bore lets the dryer finish in the cycle time it was designed for, which cuts energy use, eases wear on the motor and element, and keeps the machine out of premature failure. In other words, clearing the duct protects the plant as much as the people - and planned maintenance of this kind is consistently far cheaper than an emergency replacement, as we explain in our note on why maintenance beats replacing kitchen plant. The same logic that keeps a grease-laden extract canopy safe and efficient is what keeps a dryer drying: airflow is everything, and a clean duct is what protects it.
The principle is worth holding onto whether you are wringing an extra half-hour out of a machine at home or signing off a fire risk assessment for a building full of them. A dryer that takes longer than it used to is not asking to be thrown away - it is asking for its airway to be cleared.
Questions
The most common cause is a duct or vent that has slowly filled with lint, restricting the warm, damp air the dryer needs to expel. As airflow drops, moisture stays in the drum and cycles stretch out. Before assuming the machine is failing, clear the lint filter and have the ducting checked, as that restores performance in the majority of cases.
Yes. Lint is highly combustible and collects close to the heating element, while a blocked duct traps heat that would normally escape with the moist air. That combination of raised temperatures and combustible build-up is a leading cause of appliance fires. UK fire services consistently link tumble dryers to a significant share of white-goods fires each year.
For busy settings such as hotels, care homes and launderettes, professional cleaning of the dryer ducting every six to twelve months is the widely accepted benchmark, with the heaviest users at the shorter end. Under the Regulatory Reform (Fire Safety) Order 2005 the Responsible Person must keep this risk controlled, and most insurers ask for evidence of regular cleaning.
Very much so. Every extra metre of ducting and every bend adds friction and turbulence, slowing the air and giving lint more places to settle. Building guidance reduces the usable duct length sharply for each right-angle bend for exactly this reason. Keeping the run as short and straight as possible helps the dryer work efficiently and stay clear for longer.
Phoenix Duct Clean · by the numbers
Phoenix surveys and cleans kitchen and building ductwork to the TR19 standard - measured, cleaned and certificated, UK-wide.