Marijuana Odor Elimination with AHU Filtration

[232gulfstream]

Guys,

I have a client that operates a large condominium complex and he is getting complaints about marijuana odors migrating from 1 unit into the adjacent unit. I am in the process of analyzing the air flow and determining if the exhaust system is up to par and exhausting the required rates. In the meantime I told the client we could look at replacing the filters in the fan coil units with carbon filters to perhaps eliminate the odors before they get a chance to leave the space. Can anyone recommend a product for filtering out the odors within the space? This problem could be as simple as the smoker being out on his deck and smoke migrating into the adjacent unit when their patio door is open. Nevertheless, I want to try to exhaust every option I can for them while we are hashing out the exhaust/make-up air system.

Thanks!

 

[SAK9]

You will be better off if you try to pressurise the corridor so that odours may not spill into the corridors and increase apartment exhaust flow rates so that they may become negative with respect to the corridor

 

[EnergyProfessional]

Assuming the construction is typical, there is no real air barrier between the units. No matter what you do, the neighbors will smell smoke. I can smell marijuana on the lake when a boat passes by a few hundred feet away, and that is all open air. A non-smoker will smell smoke unless you do a really good air-sealing (hard to do after construction) and extreme high pressure differences. And then you still smell it.

Why not do the obvious and forbid smoking? What kind of area is that where smoking is still allowed? What if both parties have the window open, then there will be the smell again, even if you provide a perfect building.

 

[BronYrAur]

Why would you want to eliminate marijuana odor??? Haha. ...someone had to say it

Do you know the path from which the smoke is entering? e.g. underneath the door leading to a common corridor, etc? I don't think a filter will help too much if the smoke is entering somewhere other than the air handling unit. Pressurization would be a good idea. Does this person always leave their toilet and/or kitchen fan on thereby creating a constant negative in their apartment?

 

[232gulfstream]

It's hard to say how the smoke is getting into the adjacent unit. The place is set-up with 24/7 exhaust air in the toilet and main living area. Make-up air is provided at each end of the hallway and I guess the engineer who designed was relying on cracks around the doors for make-up air to enter the spaces. There is enough room above the ceilings in the hallway to run fresh air ducts directly into the rooms. Each rooms exhaust flow rate is only 65 cfm. How much deviation in make-up air and exhaust air would it take to create a nice negative pressure situation?

 

[MedicineEng]

I think that the only way for you to understand where is the smell really coming from is to make a smoke test and see where does it seep.
In the past I had a "similar" problem with food smell of an open restaurant seeping into mall circulation that was pissing off a particular high ranked person in our organization.
The smoke test was quite revealing of how would smell travel inside the restaurant and find its way to mall circulation and allowed us to make adjustments to mitigate the situation.

If, as others pointed out, smell seeps in through cracks and door gaps, AHU filtration will not solve any problem.

 

[FL_Gingineer]

Have someone perform a blower door test to de-pressurize the room with the complaining tenant. Then smoke test the interior and you will find where the air ingress is occurring. Then you can seal up the room, rather than try to alter the design of the HVAC system.

Note, if you go with the carbon filters, please be sure to review the static pressure drop through those filters vs. the standard (MERV 8, guessing). I estimate the dP will be 2-4x what it would be with the standard filters, which will result in a reduction of airflow. If the dP is significant enough, depending on the type of HVAC equipment and system controls, this could lead to excessively low supply air temperatures and sweating of the supply air ductwork. It is a problem we run into in humid climates, not sure of your location. Just FYI.