first-aid station; emergency medical post
A facility or room where basic emergency medical treatment is provided, often at events, workplaces, or in rural areas. Not a full hospital.
A first-aid station was set up at the sports day venue.
There is a small emergency medical post at the mountain hut.
救急車 is an ambulance, the vehicle; 救急所 is the physical station or post.
Compound of 救急 (emergency medical care) and 所 (place, station). The exact historical derivation is uncertain, but the word follows a common pattern for naming facilities.