What were they doing?

I was watching the TV the other night and I saw a commercial for some heating and air conditioning company advertising their heat and a/c home services.

They were showing everything that the heating and air conditioning specialist does.

One thing I did not know what they were doing was at one point in this commercial they were actually washing the central heating and air conditioning system unit with a water hose! I have never seen that done before. I wonder what that was for? I know hosing down your central heating and air conditioning system unit after a messy storm may be a good idea just so it isn’t really dirty, but why would a heating and air conditioning specialist be doing this? I almost wanted to call the heating and air conditioning company that was on the commercial and ask them! It really interested me. Was it just for show to look cool or was this something that has to do with heating and air conditioning maintenance that I do not know about? I really would like to find this out. Maybe I will just ask my own heating and air conditioning specialist about it the next time they come to do some work on my own central heating and air conditioning system unit. I do not know. But I really wanna know what was going on! Heating and cooling systems are a mystery to me, I only know how to turn them off, turn them on and follow up with all the heating and air conditioning maintenance that needs to be done on the heating and cooling units.

heating and cooling