Inline fan -> HPS -> Carbon filter?

Does anybody know if I can just have a carbon filter attached to a 6" CoolTube reflector with a 6" inline fan attached to the other side?

Like this.
I realize my title is opposite of my picture. The pic is right.

I am sure you could, I have seen many setups on these forums just like you have pictured.

On the other hand, I would think that it would be better if your fan was on the same side as the scrubber. This way it wouldn't have to create negative pressure in the cooltube in order to get suction from the carbon filter. I don't have any idea as to how much airflow you would be saving this way but I am sure either way is fine in the end as long as its staying cool in your setup.

Good Luck

You can! I personally have mine...... Carbon filter-fan-hps-ducting to window
Only done it like that so the fan isnt pulling warm air through it, heard it shortens the life of the fan if its pulling warm air, dont know if this is true though.

i have a 5" filter high in my tent, which then ducts to the cool tube, from the other end of the cool tube is ducting which goes out the tent and to a 450m per hr extraction fan. I need a 280m per hr fan as an inlet but it works great, my temps have dropped from the high eighties to the low 70's, and i run a 400w HPS with a 250w cfl for below canopy lighting. Tent is .76m x .76m x1.8m. Fans may be a bit of overkill but the plants are probably the biggest healthiest ones i have grown ( only 4th grow though). It will work, but you need a fairly powerful extraction. I first used the 280m fan as the outlet, but it didnt cool the tent enough.

I just want to use my t5 8-bulb setup for veg and use the HPS for flowering. It will be in a closet with the door open for the 12 hours on. And there wont be an exhaust hose.

I guess it wouldn't hurt to switch it around to find the bests temps. But I'm more worried about the effects of the heat when the HPS is directly attached to both the filter and fan.

The heat wont catch my filter/fan on fire or anything will it?

Nah mate, if the fan and filter are before your lamp the heat will be blown away from the fan and filter, its how mines set up mate and it works well for me.