Carbon Filter - Which One?

How to pick an odour filter with activated carbon? What should you keep an eye out for? This article tries to answer the most common questions growers ask when choosing a carbon filter.


What capacity should the filter have? The maximum airflow of a carbon filter is expressed in the same units as with ventilators - in cubic meters per hour (m3/h). It determines the amount of air (in cubic meters) the filter cleans in a fixed amount of time (an hour). Always pick a filter with a larger capacity than your ventilator has. If it has a lower maximum airflow, the ventilator can “overblow” the filter, which will start letting the odour through even though there is nothing wrong with it.

How much bigger the filter’s capacity can be? There’s virtually no upper limit. For example, if you use a ventilator with an output of 800 m3/h with a 4000 m3/h filter, the setup will work without a problem. The only problem will be the size of the filter - they can be very bulky at such capacities. 

Usually, growers use a filter with a 10-50% higher capacity. In the case of the 800 m3/h ventilator, the ideal filter would have a maximum airflow between 880 and 1200 m3/h. The higher the maximum airflow, the longer the lifespan of the filter.

How long will the filter last? This question is difficult to answer accurately. Usually, the manufacturers state expected lifespans between 6 and 24 months. The longevity of the filter depends on many factors:

  • Amount of carbon in the filter.
  • Quality of the used carbon and the way it’s placed in the filter. Manufacturers use special tools to even it and to leave no air between the pellets.
  • Environment - polluted (dusty) and humid rooms cause the carbon to degrade faster.
  • Pre-filter - if you have a pre-filter and clean it regularly, it prolongs the filter’s life by preventing larger particles from getting into the system.

How can I extend the life of my filter? There are not many options. All filters are doomed to a limited lifespan from the start, so it goes. However, you can at least clean the pre-filter, which keeps out the dust and other larger particles which would otherwise pollute the filter. The easiest way of cleaning the pre-filter is shaking it out, vacuuming or (in some models) even putting it in a washing machine. Replacing the pre-filter every so often is also a very good idea.

Can I extend the filter’s lifespan by replacing the charcoal? In theory, yes. However, changing the carbon is not only about taking the old out and throwing in the new. The way the carbon lays in the filter is vital to its functionality - if there are air pockets or if it's packed too tightly, the capacity will go down significantly. If you choose to replace the carbon at home, you must take into account that the filter might work, but its specification will be notably worse. 

How to install the filter? Filters are used at air intake or outtake, as long as they’re placed in front of the ventilator - this way, the ventilator circulates only clean air. If you put the filter in front of the ventilator, large particles (like dust) will catch on the pre-filter, and the filter itself will remove any odours. If you do it the other way around and the filter is behind the ventilator, all the large) particles will get into both the fan and filter, which negatively impacts the lifespan of both. 

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