Why is my cat a heavy breather?

My cat Joker does this really strange thing sometimes when he sniffs the surface of something....he comes up with his mouth open and tongue half hanging out. He looks like a panting dog... this goes on for several seconds until he licks his lips and then resumes breathing normally through his nose. It's weird because I can't seem to find a connection with the reason behind it. I first noticed him do it last year when he sniffed the surface of my black Ikea end table..I originally thought it was something on the table so I cleaned the surface off, but then I caught him doing it again the next day. So periodically I will see him do this and it doesnt look like it's bothering him, so I never really looked into it. Over the weekend I just moved into a new place which is mostly carpeted. Joker has been doing this more frequently since we arrived. I'm curious....
Anyone know why cats do this??...could it be his nasal passage gets blocked from dust like humans get stuffy noses??? (just a guess)

Cat have glands in the roofs of their mouth. It's their way of smelling a scent. Nothing to worry about.

Yes it is called a fleman (sp) response. It is a way of pulling a greater amount of the scent in. Mine tend to do this when confronting other animal scent.

Denyce

When my cats do it I call it making "the FACE!!!" Mine do it when they smell my shoes... well, duh!:p

Thanks for the replies...I never knew that!!! I wish I could snap a picture of my cat when he has that face, he looks just like a cartoon character!!!:)

Simba does that a lot too, it looks like he is smiling.

I HAVE A PIC of josie making that face . . . i'll have to post it later. IT'S SO FUNNY!