How to keep an airless room smelling fresh without chemicals?

[MsFogi]

So DS1 has just started uni, he has a nice room and he is happy but it has a pretty small window and is very warm. We have a fan in there to circulate the air a bit, but it is pretty airless. Now he’s been in the room a few days (along with shoes and all his worldly possessions) he tells me that a he is finding it difficult to keep the room smelling fresh. I don’t want to fill the place with chemical air fresheners/neutralisers given that it is where he is sleeping/studying - can anyone suggest how he can get the place smelling ‘fresh’ without the ability to get any more air in through the window (which he is leaving open all the time). To note opening his door won’t help much given that it only opens onto an airless corridor and he’s not drying any laundry in the room.

Air purifier?

How about soe bicarb in a jar with some lavender drops.

Tumble drier sheets in pillows.

I find doing the cleaning with a damp cloth with a dab of Zoflora really makes a huge difference. I wipe down the rads, door frames, light switches , lamp shades etc

Get the fan as close to the window as possible, facing the room so it's pulling the air in from outside

Doing that along with keeping his door open a crack should help

Is there a door out of the corridor to anywhere? Even if just a stairwell. If that can be left open even a crack, air will move

Hang tumble drier sheets in front of window

Bicarbonate in a bowl to pull in any odours

Can he leave his shoes outside his door? If not, use foot powder / shoe spray every night

Needs an air purifier/ ioniser.