Drain lines for HVAC

Yesterday I came across these drain lines. Can someone tell me what this small section of pipe with the tape on the end is for? I have not seen this before, is it some type of improper vent? I don’t get it, can someone set me straight on this

A clean-out, that should be capped.

Thanks, I new it had to be something simple I always seem to over thing things

I found another one of these today and after further investigation I discovered that this is a vent and it is done right

What is the vent for? It looks like a clean out for the trap they put in to the drain line to me and I agree it should have a cap and not tape.

none pictured are correct…

best practice: condensate drains should be installed at primary and secondary, trapped and anti-siphon vented downstream from the trap, advise insulating drain lines when installed in the attic or crawl

though sometimes artful the smooth wall prefab trap Chris exampled, if they’d only put the vent on the proper side, is also preferred to the cut and glue creative concoctions often encountered and unglued…

condensate drain diagram.jpg