A friend started smoking again. But he already knows that.

Why don't you turn it around? You have a cat right and I bet your house doesn't smell.

So just say to them next time you are together that you are going nuts because nothing you use can get rid of the pet smell in your house and a close friend mentioned they could whiff it as soon as they walked in and ask them what they recommend. If they something like Febreeze (or whatever) then next time you are out - buy them a bottle and say seeing as you got yourself some you bought them some too as a thank you.

Also then delight in telling them of some of the other things you tried (not that you have but then you can give lots of suggestions too )

I would just avoid them.

I bet it does smell of cats to someone who doesn't have any. Same as houses with dogs have a smell. I've tried all subtlety but this is beyond background smell. I will just have to wait for a suitable spot in the conversation, or just carry on not inhaling

Buy some dollar store airfreshensers.
Put them in a box on the front step.
Knock on door.
Run.

Or come striahgt out and say "ooooh I can really smell dog today - does one of them have an ear infection or something its very strong????"

if they say no then its a "well I reckon it's time they had a bath, maybe the warm weather is taking its toll"

Although all that considered I kew some people down in Drumheller whose house looked like an episode of hoarders and stank too. super nice people but seriously???? If they don't think thats a problem then I don't think anything you can do will be able to get them to fumigate everything thats in there.

I'd stay away and if they mention it say that for some reason the pet smell really aggrevates your allergies?!

are they living in an old house? Ours has a smell and nothing we have done so far seems to get rid of it. It's just old.

How old is old? I didn't think there were old houses in Vancouver?

My last one in the UK was built in 1754 and didn't smell particularly. A little damp in some rooms but we also had a dog.

A damp dog? They are quite whiffy.

Indeed....unavoidable generally with a Springer.