Most people have never looked. The dryer goes against the wall, a duct disappears behind it, and that is the end of the relationship.

It is worth ten minutes. You cannot tell whether the vent is working without seeing where the air comes out, you cannot describe the problem to anyone over the phone, and if the run turns out to terminate somewhere it should not, that is the kind of thing better found on purpose than by accident.

Start at the back of the dryer

Pull the machine forward. Behind it is a short flexible connector, the transition duct, running from the exhaust port to an opening in the wall, the floor or the ceiling. That opening is where the concealed run begins.

Two things to note while you are back there. First, the condition of the transition duct itself. Crushed flat, kinked, or pulled partly loose is a problem you have just found without looking for it. Second, the direction the duct enters the structure, because that tells you most of what you need next.

Then walk the outside

The reliable method needs two people and five minutes. One person runs the dryer on a heat cycle. The other walks the perimeter of the building.

You are looking for a hood roughly four inches across with a hinged flap or louvers, usually somewhere between knee height and shoulder height, and generally within ten or twelve feet of where the dryer sits inside. But you can often hear and feel it before you see it, and the giveaway most people miss is smell. A running dryer pushes out warm, damp air carrying the scent of whatever detergent or dryer sheet is in the load. Follow that.

Other tells: lint caught at the edges of the hood or streaked on the wall below it, and a patch of siding or stucco that stays discoloured from years of warm moist air.

One local note. National guides will tell you to check the basement. Almost nothing here has one, so on a typical slab-built South Florida home the run is going sideways through a wall or up through the roof, and nowhere else.

How to tell a dryer vent from everything else on the wall

This is where people get it wrong, because an exterior wall can have five or six openings on it and they look broadly similar from a distance.

• A dryer vent is about four inches across, has a damper flap or louvers that move when the dryer runs, and has no screen or mesh behind it. Screens are not permitted on a dryer termination because they clog with lint.
• A bathroom exhaust vent is a similar size and also has a flap, which is why it gets confused. It blows humid air but no lint, no heat to speak of, and no detergent smell, and it runs only when someone flips the fan switch.
• A range hood vent is usually larger, often rectangular, and sits high on the wall near the kitchen.
• An air conditioning or fresh-air intake is screened or louvered and pulls air in rather than pushing it out.
• A plumbing vent is a pipe through the roof with no cap flap and no airflow you can feel.

The definitive test is the one above. Run the dryer, and see which one starts moving air.

The four places it usually comes out

An exterior wall. The most common configuration and the best one. Short run, easy to inspect, easy to clean.

The roof. Standard where the laundry room sits toward the middle of the floor plan, which describes a lot of newer single-family construction in western Broward and Palm Beach County. The duct goes up inside a wall, across the attic, and out a cap. If you have walked every exterior wall and found nothing, this is almost certainly your setup.

A shared shaft. Common in mid-rise and high-rise condo buildings. Individual units vent into a riser serving a whole stack, and there is no hood of your own to find outside.

Somewhere it should not be. Occasionally the run terminates in a garage, a soffit, a crawlspace or the attic itself. None of those are acceptable. A dryer moves a serious amount of moisture along with the lint, and putting both into an enclosed part of the structure causes damage over time and raises the fire risk. If that is your situation it needs correcting rather than cleaning.

Condos and high-rises, where this gets harder

If you are in a building and cannot find a termination, you may not have one, and that is normal rather than a fault.

Buildings handle it several ways. Some run each unit horizontally to the nearest exterior wall, which is where the very long runs come from in older coastal buildings. Some terminate under a balcony soffit, so the hood is above your head on the lanai ceiling and nobody ever looks up at it. Some feed a vertical shaft shared by every unit in the stack, sometimes with a building-owned booster fan at the top.

The shared-shaft case matters most, because responsibility splits. The association typically maintains the shaft, and the section inside your unit is yours. That is how a run ends up half cleaned with everyone believing it was handled.

Three things worth doing: ask the property manager or building engineer what the configuration is, ask specifically where the association responsibility ends, and ask whether building plans are available. On a stack system, also ask when the shaft was last serviced.

If you rent

Trace it as far as you can see, and stop there. Do not open walls or remove exterior covers on a unit you do not own. Report weak airflow, long drying times or a burning smell to the landlord or management in writing, which puts the maintenance obligation where it belongs and creates a record if it goes unaddressed.

The test once you have found it

Run the dryer on a heat cycle and go to the termination. You should feel strong, steady airflow and see the flap held open rather than fluttering. Weak flow, a flap that barely moves, or nothing at all means the run is restricted, and the machine is almost certainly not the problem. See how often a vent should be cleaned.

While you are there, look at the hood itself. Along the coast, salt air corrodes dampers, and one seized part-way shut restricts airflow even when the duct behind it is clear.

Write it down while you know

Photograph the termination, note roughly where it is and how far it runs from the machine, and keep it somewhere you will find it. You will want it the next time you book a cleaning, sell the place, or try to explain the problem over the phone, and you will not want to do this search twice.

One safety note

Do not go up on a roof to inspect a cap. Tile roofs in particular break under foot and the repair costs considerably more than the cleaning. Roof terminations are a job for someone with the right equipment.

If you cannot find it

Condo buildings, older homes with additions, and anything that has been renovated more than once are genuinely difficult, and there is no shame in not finding it. Tracing the run is part of the job for us, and knowing where it goes is the first thing we establish before cleaning anything.