Most dryer vent problems arrive slowly: longer drying times, a laundry room that runs warm. A few signs are different. They point to heat building where it should not, inside the vent or at the back of the machine. NFPA research on home fires involving clothes dryers identifies dust, fiber, and lint as the leading item first ignited, which is why these particular signals earn an immediate response rather than a note on the calendar.
A burning smell during or after a cycle
Lint ignites easily, and a burning smell while the dryer runs, or one that hangs in the room after the cycle ends, usually means lint somewhere in the system has gotten hot enough to smolder. It is not the ordinary smell of warm fabric or a dryer sheet. A burning smell is sharper and more acrid, and it belongs in the category of things you handle now. Shut the dryer off, unplug it if the outlet is within safe reach, and have the vent looked at before the next load.
Notice where the smell is strongest. Concentrated behind the machine, it points at the transition hose and the vent connection. Filling the whole room, it points further along the run. Either way the smell itself is the signal, and it calls for the same response.
The dryer feels unusually hot to the touch
Put a hand on the top and the sides partway through a cycle. Warmth is normal. A cabinet too hot to keep your hand on, particularly near the back where the vent connects, means heat is collecting somewhere it should not. The CPSC ties that pattern to lint accumulating in the exhaust duct, which restricts airflow and lets the machine overheat, and the strain shows up across the whole dryer rather than only inside the duct.
The dryer shuts off on its own mid-cycle
Most dryers carry a thermal cutoff that stops the machine when internal temperatures climb too far. If yours has started quitting partway through cycles with no other explanation, that cutoff is doing its job against a heat buildup caused by restricted airflow. Resetting it and starting another load leaves the cause untouched and asks the same safety device to save you again.
Scorch marks or discoloration near the vent connection
Look where the transition hose meets the back of the dryer, and at the wall or floor the duct passes through. Discoloration, a yellowed or brown cast on the hose, or scorching on nearby material means heat has already reached a level high enough to leave a mark. That takes sustained temperature rather than one hot minute, which puts this near the top of the list.
Lint visible anywhere around the dryer
Lint clinging to the back of the machine, gathering at its base, or collecting around the hose clamp is more than housekeeping. It means lint is leaving the duct partway along rather than exiting at the cap, which points to a gap, a loose clamp, or a section that has separated. Paired with heat or a burning smell, lint outside the duct is a reason to have the full run checked rather than swept up.
When to stop using the dryer
A burning smell, a cabinet too hot to touch, repeated mid-cycle shutoffs, or scorching near the connection all mean stopping use now rather than booking a cleaning for a convenient week. Each of them says heat has gone past ordinary operation, and another load keeps that condition running. One sign alone may have a simple explanation. Two together should be treated as urgent.
If any of this describes your machine, unplug it and leave it off until the run has been inspected. Dryer vent cleaning clears the full length from the transition hose to the termination cap, which is what removes the fuel rather than the symptom. Until that happens, hanging a load outside costs you an afternoon, and running one costs more than that.