I don't even know how you got an understanding of that sentence.
I'll enlighten you. hydrocarbon (gas) is burned with a stoichmetric ratio of 14.7parts ambient air to one part of fuel, creating CO2 and the remaining pollutants Nitrides of oxides N0x, carbon Monoxide and little HC, the HC and CO is catalytically converted into water vapor using platinum for the oxidation process and palladium and rhodium for the reduction process.
Any other questions?
i'm a licensed ASE certified technnician, and have an EA CA smog License.
I've been diagnosing smog failures and vehicle trouble shooting for seven years.
I've been working on cars for roughly 25 years.
If you really want i can break down the chemical process for you, but i'd rather you look it up, which is what you should have done before you question something you aren't educated on.
If you'd like to discuss a carb'd 67 lincoln then i'll change my statement, but ALL new cars when running properly emit less than the 10 parts per MILLION of HC,negliglible NOx and 0.00% of CO.
AMBIENT AIR can contain more than what comes out your tailpipe.