mac mini miminum clearance

Does anyone know (in inches or cm) how much clearance a mac mini needs on all sides to operate safely? I'm quite amazed that after searching for 30 minutes I haven't found any definitive answer. It must need some "breathing room."

You would think that Apple would provide this in its documentation. Or is this just something Apple doesn't want to be held to in a potential lawsuit? All my other expensive electronic equipment provides very precise clearance specifications for operation.