Results have been 100% positive in AC mode
We should have results for it in the heat mode by Christmas.
However, it's not in any AC "vent" hoses...I don't think HVAC systems have vent lines! It's little block of stuff that sits in the air return...lasts up to 5 months. If it works as well in the heat mode as it does in AC mode, it should be available sometime in the first quarter of next year.