Indoor Carbon filter/ventilation problems

[Cheesehead]

So I am 6 weeks into my first grow. Everything is going well except for my carbon filter. So for the first two weeks of my grow, my ventilation was perfect. I had negative pressure in my tent so no air was seeping out and the airflow was strong. At 3 weeks, my airflow had been cut down to a fraction of what it was. I read online that your carbon filter can become clogged if humidity is too high. So now, 6 weeks in, my carbon filter is still having airflow problems. My humidity in my tent is at a pretty constant 50-55% which I know is a little high for flowering but my filter is obstructing airflow. Temp is also staying a little high at 77-80 but again my filter isn't producing enough. My fan is a Ventech 6" inline duct fan which is rated at 440 cfm so I know it's not the fan(Also I have a speed controller and it's set at 100%). My filter is a 4" ventech carbon filter rated at 210 cfm(I know 4" filter and 6" fan is not supposed to go together but I have a reducer and I know that's not the problem either because I've had the same set-up since day one). My ducting isn't completely straight but it's the same set-up I've had since day one and for the first two weeks of my grow, I had excellent airflow. So my question is, should I go for a new filter or what can I do to fix this?

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Is there an optimum level of humidity that carbon filters can function properly in?

 

[namvet25]

How old is your filter?,and does it have a pre filter sleeve on it.Humidity should not affect the filter as far as I no.

 

[Cheesehead]

Filter is brand new, I bought it new 7 weeks ago. Yes, it has the white pre-filter on it. I think I'm just gonna have to get a higher quality filter...

 

[namvet25]

That's weird,even a cheap filter should last longer than that.Have you tried it without the prefilter on?A name brand filter might be your best bet.

 

[Son of Hobbes]

So I am 6 weeks into my first grow. Everything is going well except for my carbon filter. So for the first two weeks of my grow, my ventilation was perfect. I had negative pressure in my tent so no air was seeping out and the airflow was strong. At 3 weeks, my airflow had been cut down to a fraction of what it was. I read online that your carbon filter can become clogged if humidity is too high. So now, 6 weeks in, my carbon filter is still having airflow problems. My humidity in my tent is at a pretty constant 50-55% which I know is a little high for flowering but my filter is obstructing airflow. Temp is also staying a little high at 77-80 but again my filter isn't producing enough. My fan is a Ventech 6" inline duct fan which is rated at 440 cfm so I know it's not the fan(Also I have a speed controller and it's set at 100%). My filter is a 4" ventech carbon filter rated at 210 cfm(I know 4" filter and 6" fan is not supposed to go together but I have a reducer and I know that's not the problem either because I've had the same set-up since day one). My ducting isn't completely straight but it's the same set-up I've had since day one and for the first two weeks of my grow, I had excellent airflow. So my question is, should I go for a new filter or what can I do to fix this?

- - - Updated - - -

Is there an optimum level of humidity that carbon filters can function properly in?

My fan is a Ventech 6" inline duct fan which is rated at 440 cfm so I know it's not the fan(Also I have a speed controller and it's set at 100%). My filter is a 4" ventech carbon filter rated at 210 cfm(I know 4" filter and 6" fan is not supposed to go together but I have a reducer and I know that's not the problem either because I've had the same set-up since day one).

Part of the problem here is your fan isn't properly matched to the filter. That 210 CFM rating is rated by the manufacture for optimal performance; you're more than doubling the suggested optimal airflow. Moving air through a carbon filter too fast actually reduces the effectiveness of the carbon. Each particle or granule of activated carbon provides a surface area full of pores for impurities to be exposed to. As the impurities passes through the carbon, they get adsorbed (trapped) in the porous holes through chemical attraction. There has to be sufficient contact time for that adsorption to occur, so if you're moving air too fast, that's happening at a reduced rate. If you moved air too slowly, again you're not effectively pulling the air through the carbon bed for filtration.

The efficiency of a carbon filter depends on several things:

• Airflow CFM (Cubic Feet per Minute.) The fan attached to your carbon filter must be of the appropriate CFM value to be as effective as possible.
• Molecule size of organic impurities (larger molecules are adsorbed better than smaller molecules.)
• The pore size and distribution of the activated carbon (varies by method and manufacturer.)
• Temperature - lower ambient temperatures tend to adsorb smells better than higher ones. The reason for this is at higher temperatures, the VOC (Volatile Organic Compound) molecules start breaking down into smaller molecules. Activated carbon adsorbs larger molecules easier than smaller, so maintaining the temperature keeps them in a more efficient state for adsorption.

As to your question on the humidity, this was asked by another member the other day and from the information I gathered; it takes around 80%+ sustained humidity to begin reducing the effectiveness of the carbon, as what's happening is the water molecules start to gather on top of the porous carbon, which reduces the ability to adsorp the VOC's.

One thing you can try is to remove the filter from the in-line setup and shake and tap the crap out of it. Since the distribution of the carbon can vary (possibly bigger chunks sitting on smaller chunks or something to that effect,) sometimes shaking it up can redistribute the carbon.