Air purifier in grow space question.

Hello everyone, I am about to start another run in my 2.5’x6’ closet (ceiling is 8’).
I have a small air purifier that uses a Hepa filter with a thin carbon screen in front. It came from Lowes or Home Depot and is suggested for small rooms. It’s a stand alone unit and not connected to my exhaust.
My question is should I use it? And if so, should it be inside the closet or outside in the room?
I have a 6” exhaust fan at the top of the grow space and until now been relying on a passive intake through a 1” space between the door and floor.
i decided to add 3 round holes, each about 3” in diameter…..just another passive opening into the room where the closet is located.
I probably should have asked if the new intake holes were needed but didn’t.
Anyway, I can see the benefit of purifying the air within the closet but can also see value in treating the main area which is the source of all new air.
Thanks for weighing in.

If you're really concerned you want the closet sealed with a hepa filter on your passive intake and a decent extraction fan with a carbon filter.

rootforme said:

If you're really concerned you want the closet sealed with a hepa filter on your passive intake and a decent extraction fan with a carbon filter.

Click to expand...

Thanks for the info. I’m not really concerned about anything in particular….just wondering where the air purifier unit would do me the most good, inside the closet or outside near the passive intake.
Since u seem fairly knowledgeable, I’ll ask you a more basic question: given a space my size, how large does my passive intake opening need to be?
The space under the door is about an inch high and runs the length of the door, which is 30-32”.
I drilled 3 holes on the side that opens into the same room….holes are 3” in diameter.
My exhaust fan is pretty beefy and is rated for a space much larger so I never run it on full power.
Any thoughts here would be great.
Thanks again.

Bullmark said:

Thanks for the info. I’m not really concerned about anything in particular….just wondering where the air purifier unit would do me the most good, inside the closet or outside near the passive intake.
Since u seem fairly knowledgeable, I’ll ask you a more basic question: given a space my size, how large does my passive intake opening need to be?
The space under the door is about an inch high and runs the length of the door, which is 30-32”.
I drilled 3 holes on the side that opens into the same room….holes are 3” in diameter.
My exhaust fan is pretty beefy and is rated for a space much larger so I never run it on full power.
Any thoughts here would be great.
Thanks again.

Click to expand...

A 1" x 30" vent plus 3x3" diameter holes should be more than enough passive intake. Though if you're looking to filter, having a space under the door is awful hard to rig with any kind of filter because you'll be opening/closing that door. I have a layer of MERV13 over my intakes to filter dirt/dust/etc. and it is more than enough to capture what it needs. Though any filter will also slow the airflow a bit too.

LeastExpectedGrower said:

A 1" x 30" vent plus 3x3" diameter holes should be more than enough passive intake. Though if you're looking to filter, having a space under the door is awful hard to rig with any kind of filter because you'll be opening/closing that door. I have a layer of MERV13 over my intakes to filter dirt/dust/etc. and it is more than enough to capture what it needs. Though any filter will also slow the airflow a bit too.

Click to expand...

I have quite a bit of pet hair and carpet fibers that get in through the current space under the door….I was thinking about eliminating it somehow. I could add as many of the 3” holes as needed. I’ll def use a layer of MERV13 over the holes as well.

Bullmark said:

I have quite a bit of pet hair and carpet fibers that get in through the current space under the door….I was thinking about eliminating it somehow. I could add as many of the 3” holes as needed. I’ll def use a layer of MERV13 over the holes as well.

Click to expand...

You're better off with 1 6" hole over multiple 3" unless money is no object and you don't care about buying multiple filters but I don't know if a 3" inline hepa filter exists so additionally I would stick to standard size holes like 4,6,8 inch, and i'd only make 1 for intake and 1 for exhaust. Additional holes increase your chances of problems so stick to the 1 in 1 out method and make the holes big enough for decent air extraction. I would do 6".

Having a hepa filter in your room is a great idea. Things like dust mushrooms or just nylons on your tent/grow space intakes really help reduce pet hair and dust, but a hepa filter also reduces spores floating around the room and landing on your buds. Best is one that cycles the air in your lung room 5 times per hour, but use what you have. A hepa filter is a great tool to use if you've had or are worried about PM or botrytis.

Here's the MERV13 I bought... 20 square feet for 20 bucks, and that should last a good long time. I've used about 1 square foot of it so far. I've used it as either a single or double layer. Pretty cheap and good for lots of grows.

rootforme said:

You're better off with 1 6" hole over multiple 3" unless money is no object and you don't care about buying multiple filters but I don't know if a 3" inline hepa filter exists so additionally I would stick to standard size holes like 4,6,8 inch, and i'd only make 1 for intake and 1 for exhaust. Additional holes increase your chances of problems so stick to the 1 in 1 out method and make the holes big enough for decent air extraction. I would do 6".

Click to expand...

i understand one larger hole being better than several smaller ones….but I’ve already cut 2 small 3” ones. It started out just as a conduit for my elec cords but then I realized how much debris was entering the space from under the door. I figured I could screen or filter the round holes better than under the door.
When you say in-line hepa filters I’m not sure that’s what I have going on. I have a stand alone air purifier, with a hepa and carbon filter. It’s a square unit about 18”x18” and about 8” deep. It would sit by itself (not attached to anything) either in the grow closet or outside the closet in the main room.
i just didn’t know if it would be better to have it inside or out….what’s your opinion on the location??
Thanks for the info and taking the time to reply.