How do I nicely tell my coworker to not microwave his tuna sandwiches in the Break room?

In one building we had a cooktop surface in our kitchen as well as a microwave and a toaster oven. We had only one person who used the cooktop. And what did he make most of the time? Fish, heavy on the garlic and aromatic spices. He thought it was yummy, the rest of us, not so much. Management sent a generic email, to everyone, asking that no once cook seafood or use garlic, and in fact it was preferred that the cook top not be used at all. Even though it was meant for only one offender they sent it to everyone. He stopped.

Leave him alone. Sit somewhere. Else!

I don't know why people always want to 'tell' others not to do things. Have you thought of 'asking' him instead?

You'll probably have to get management to crate a policy on this. I've worked in several offices where microwave popcorn was banned because it got burned one too many times and stenched up the place.

Throw some raw eggs & cheese behind the coke machine. In a few days the breakroom will stink so bad it'll drown out the smell of the nuked tuna.

Talk to HR. All law firms banned microwaving popcorn at least a decade ago because of the stink. Most people aren't so weird that they microwave tuna sandwiches but they should be able to set a policy just for this weirdo. If all else fails, tell him microwaving tuna rancidifies it.

Tell him he can heat it by sitting on it

not rnuch you can do about it, rnaybe you can offer hirn sorne of your food, once he sees how rnuch better it is he rnight rnake that instead

Maybe he doesn't like the smell of your popcorn, either.

Just tell him. "Hey do you have to microwave your tuna sandwitches? The smell isn't very good."