My friend bought a vented dryer but didn't buy a vent. I did ask her if it needed one but she insisted that if it was needed it would have been supplied.
Six weeks later, her previously clean, dry house was covered in black mould.
I appreciate that not everyone needs a new vent on their dryer but manufacturers should put a big warning sticker on vented dryers.
She dumped the dryer as she didn't want to open a door or window to trail the hose out and bought a condenser version. It helped a lot but even a condenser will cause a bit of damp unless a window is opened in the room.
There's a big difference between drying indoors and airing indoors. I was told by a building inspector that if you have to dry indoors you need the room ventilated to allow the damp to escape. He said airflow was more important than anything else.
His recommendation was to do an extra or higher spin, dry outdoors as much as possible, windows open in the room being used and air only in warm areas. He said people use 'airers' to dry should be aware of the health issues with damp. He recommended that the quickest, cheapest and most damage-free way was to drive airflow through washing on an airer with a fan, as a PP has mentioned. As long as the door to the room is closed and a window open it shouldn't cause a damp or mould problem. when the washing is nearly dry, air in a warmer room.
I've always dried outside whatever the weather but mobility is now an issue for my going in and out so frequently if there are showers. I ended up inheriting a heat pump dryer (and found out the hard way why the owners were not keen on it). It is very economical - it tells me the usage which is about .6KWH for almost 2 hours for a load of cottons.
However, it uses such low temperatures that it starts smelling really unpleasant. I've tried running it empty and it has a distinctive smell like nothing else and definitely not musty clothes or washing that hasn't had enough detergent added). I've also replaced filters.
The only cure I've found is to run it only on the warm air setting. It appears that using low drying temperatures, particularly if it doesn't get used regularly, causes the smell. It generally uses the same amount of electricity as drying times are much faster.
I've read several posts here complaining of a smelly heat pump dryer and can only conclude that running at such low temperatures causes a microbial problem inside the machines.
I'm still not a fan of tumble-drying as the filter filling with all that fluff and clothes feeling more worn out puts me off.