It is common for fan heaters to be brought into workplaces! Whilst this is not an issue, when plugged into extension sockets can lead to overloading extension leads.
Most extension leads are rated at 13A, although some are 10A, the rating being marked on the extension itself.
If a fan heater rated at 8-9A is plugged into an extension lead, with other appliances already plugged in, it can overload it causing it to overheat and possibly cause a fire.
It’s never good practice to plug high power rated appliances into extension leads or indeed plugging extensions into other extensions.
In addition, it’s not good practice to use block adapters as they are also easily overloaded and the 2 way adapters are not fused.
Always plug heaters directly into wall sockets to avoid the problem of overloading extension leads.