smell in HVAC system; oh crap

I can't turn on the heater or the AC without getting a strong smell over the entire house.
All the house vents and one of the forced air units is in the attic. The air from my grow blows into the attic, but the air returns are inside the house where it does not smell.
Even the smell in the attic itself is not that strong. I have changed all filters in the in the HVAC system and have been running a carbon filter in the attic, but it has not helped.
Can the smell soak into the vents like osmosis?
I can NOT have friends or family over during the winter and during summer, when I use the AC.
Please help

is there a vent in your grow room? if not then you might be getting particles dropped into the house vents in the attic when the system is off but when you turn the blower on are pushed out into the rest of the house. if not that i would think that the problem would be your filter going into the attic, your duct work is probably piped through there for some rooms and leaks in the duct work are getting smells pushed into them by the positive pressure created by your filter and being blown around the house. Hope this helps.

burnonedown21 said:

is there a vent in your grow room? if not then you might be getting particles dropped into the house vents in the attic when the system is off but when you turn the blower on are pushed out into the rest of the house. if not that i would think that the problem would be your filter going into the attic, your duct work is probably piped through there for some rooms and leaks in the duct work are getting smells pushed into them by the positive pressure created by your filter and being blown around the house. Hope this helps.

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If you have a heating/cooling register in your grow room and it is not fully sealed it will create an overpressure condition in your grow room.

This can allow the scents to be exuded under doors, through cracks in walls, etc...

You might also have a damaged or torn duct on the supply side of the HVAC system between the filter and the unit.

without seeing the system there is no way to be completely sure though.

If the smell is coming from your vents, chances are you either have a return register in your grow room, or a decent-sized leak in your return ducting in the attic (this would cause the danky attic air to be pulled into your system. Go up there and listen with your furnace fan switched to "on" at the thermostat. You should be able to hear it hissing (or a low-pitched sucking sound if it's a BIG leak.