A few thoughts on this @Standingupstream
Disabled toilets are called accessible toilets now because are accessible for those that need them. This would include this scenario. Everyone needs a better ventilated toilet than this office one. However, if the man is physically unable to get to the secluded accessible toilet in time, then he will need to use the unisex toilet in the office.
I am surprised the accessible toilet is secluded as they pose a risk to safety. They should have a pull cord for emergencies and it is best they lead on to a high traffic area. For those saying accessible toilets have to have a radar key - they do not, but radar keys have been used to reduce sex, drugs and other misuse that such private, mixed sex toilets attract.
There is a hygiene problem in that flush plumes cover the sink and handle inside smaller unisex toilets. Men don’t wash their hands as often as women so that’s a problem too (scientifically proven).
The reason traditional single sex toilets within a single sex washroom have a gap below and above the doors and partitions is that they are best for health and safety - ventilation, cleaning, supervision and prevention of misuse. Natural ventilation is better than mechanical ventilation.
But when there’s only one toilet in the office that is going to be unisex. However, like pp have said, this needs to be ventilated sufficiently. https://www.hse.gov.uk/pubns/indg293.pdf
The toilet at present is causing health issues. Woman are affected. They are more likely to need a toilet due to biological reasons. Some women may need a toilet close by because of menstrual flooding etc. So the problem needs sorting. The toilet is being made inhospitable for long periods of the day.
If a window can not be put in, then the mechanical ventilation needs to be upgraded. It needs to be on a timer so it goes on for a longer time to clear the air. The lock must show that the toilet is engaged but have a way of being opened from the outside (outwards) if anyone is in difficulty. The door must be kept shut at all times. It would be best that the door is not too resistant to sound in this case in case the occupant needs help. Rules about keeping the door closed etc could be put in writing on the door.
There are building regulations on toilets and ventilation rates, if you need to go down this route.
I don’t know what country you are in but for England the Approved Document for toilets is:
https://assets.publishing.service.gov.uk/media/6901feb971b575684c3cf7c4/ADT_2024_rev16Jun25.pdf
The ventilation one is called Approved Document F and can be googled too.