What exactly are "mobile air conditioning units" which are used in some ads for apartments in Paris?

Their name says what it is. You can move them from one room into another as most of them are on wheels. I have one in my home office and my experience is that they do cool but don't dehumidify and don't filter the room air. A split level system works totally different.

A couple years ago in Venice, the place we stayed (sm. apt., 2 BRs), had a mobile AC unit. The place was not "wired" for AC, so this was an inexpensive alternative for the owner to supply AC to tourists or whoever. It connects to a window, has a long hose, and it's totally portable, from room to room. Cool what you need, then move to another room. Worked great with our 2 kids who were in the other bedroom than us. We were in Venice in July, so it was a very welcome relief at the end of the day and thru the night.

Happy travels!

Lots of hotels and stores have mobile ac units in Europe. They are about 2 feet tall and have a hose that drains the water to the outside. Some stores actually have the hose going out their entrance doors.

My family and I are going to Paris June 16-24 and have booked an apt with no AC. We have stayed in Paris once before in June and had a Hotel with AC but never used it. Where can one purchase a Port. AC unit if we were to find we need one?

You could buy a 'climatiseur' at Darty's, a hardware/electronics/appliances store chain. Would you really purchase one for a week's worth of use? They aren't inexpensive (think E500-E1100+) -- what would you do with it at the end of your stay?? Donate it to the apartment??

Probably we will hope for the best and find ways to deal with the heat if it comes again this year. I would not mind donating a fan to the Apt. but probably not a 500E AC.