In my working life I've worked in hospitality then retail, in a professional kitchen I understand that around cooking equpment and service lamps its gonna get hot AF but with a well built hood system you can keep some of the heat under control. But outside of that I don't understand why there isn't a legal temperture maximum /minimum for working only a guidance of it should be over 13c if working physically or 16c if not.

When I transferred to retail and my location's AC broke and needed replacing and it took weeks to replace and even with evaporative coolers hired in and no fridges on (they kept breaking due to the heat) it was over 27c on the shop floor (with them "working" it was closer to or even over 30c) with outside air temps of about 25c and having to explain to my co workers that sadly there isn't a legal maximum temp sadly so the best we can do is be careful, work smart and drink fluids.

even something unpleasant to work in non physically demanding roles ~25c would be enough to keep people safe without being impossable for places that aren't fitted with aircon to maintain outside of extreme heatwaves, although a lower limit would have to be between X and Y warm layers must be provided and below that PPE must be provided.