glade air freshener????...realy...not
heres another write up urban garden magazine did on filters and how they work.
Carbon filters are used by indoor gardeners to purify the air entering and exiting their indoor gardens. Carbon filters can remove pollens, bugs, molds, pathogens and unpleasant odors from the air.
Join us as we take a peek inside your carbon filter to see whats really going on!
Carbon filters contain activated carbon (also known as activated charcoal.) Activated carbon is specially processed from charcoal at extremely high temperatures. This process gives the carbon a very high level of microporosity or extremely fine porosity, visible only with the aid of a microscope. When we refer to carbon as being activated or active, we are essentially referring to the existence of this microporosity.
To the naked eye, the contents of your carbon filter doesnt look that exciting just a pile of carbon granules. The real magic of activated carbon only becomes clear when it is viewed under an electron microscope. The key lies in its super-high surface area, visible as labyrinths of hills and gullies, perhaps only separated from each other by a few nanometers. Amazingly, just one ounce of activated carbon has a surface area in excess of 150,000 feet² (or about four football pitches.) These vast amounts of additional surface area created by these micro-textures dramatically increase the carbons ability to absorb molecules.
So how do you measure the efficiency of a carbon filter? Well, it really depends on what you want to use it for. Different types of activated carbon suit different applications. Manufacturers of carbon filters sometimes refer to the ability of the activated carbon to hold iodine as a measure of its efficiency. However, when using a carbon filter in a real indoor gardening scenario there is a lot more going on than in a lab testing for iodine absorption.
Airflow and Effectiveness
The big challenge for a carbon filter in an indoor growing scenario is the speed of the air-flow over the activated carbon. The activated carbon bed is being subjected to extremely high airflows with small contact times. In fact, activated carbon industry experts are often astounded that the filters designed and used in indoor gardens are 100% efficient and operate for long periods of time. Many growers use extraction fans to replace old air with fresh air in their indoor gardens. This helps to insure sufficient levels of CO2 and keep the gardens temperature and humidity within an acceptable range for healthy plant growth and bloom. Often a carbon filter is inserted inline into the extraction system. But many novice growers fail to realize how much extra resistance is created by their carbon filter around 20%. That means the CFMs of any extraction fan connected to a carbon filter are reduced by 20%! (Not to mention the resistance caused by ducting.) This is why its really important to over-spec your extraction equipment.
Key Quality Factors of Carbon Filters
- The actual surface area of activated carbon.
- The meso and micro pore surface of the carbon.
- The macro structure of the carbon particle.
- Packing. Correctly packed carbon does not settle and allow air to pass through the filter untreated.
- How the above factors affect the airflow around each particle and ultimately through the carbon bed.
Filter Fact
Just like us, carbon filters gain significant weight during their lifetimes! The more weight gain the better. Highly effective filters can gain 12-15% of thir base weight. Low quality filters only gain 2-3 % weight.
Non-uniform carbon particle shapes and sizes create extra turbulence when air moves over them. This contributes to increased entrapment of molecules.
To imagine this, picture some waves reaching a small beach.
Low turbulence = calm lapping waves.
High turbulence = huge crashing breakers on to rocky shore line.
Now try to imagine this within an airflow situation. Which scenario do you think works best? It turns out that low turbulence is not what youre after. The more the air swirls and gets pounded against the carbon the greater the removal of organic molecules. Smooth laminar airflow is not the aim of the game.
Humidity
Remember carbon filters effectively stop working in very humid environments! This is because water coats the activated carbon matrix, which simply means that no carbon surface is available to catch organic molecules. Keep your gardens relative humidity well below 82%.
Maintain the Pre-Filter
That white wrapping around your carbon filter isnt just there to make it look pretty. Dust and larger particles can physically block the activated carbon surface matrix. The pre-filter is there to protect your carbon filter. Never run your carbon filter without a pre-filter and make sure you wash it every three to four months.
Fly with the Eagles
The higher up you position your carbon filter, the more efficient it will be. Warmer air will rise in your indoor garden. It has more energy and therefore binds with more organic molecules. You also want to be removing the warmest air from your garden in order to cool it most efficiently.
Depending on the filter / fan / humidity combination and the quality of the filter they can be effective in an indoor garden for between eight months to two years. Some stores offer carbon filter re-packing services. Check with the manufacturer of your carbon filter to see if they recommend this. Some carbon filters contain uniform pelletized carbon which is straightforward to refill whereas others are filled with a proprietary blend of particle sizes.
The optimum size for an activated carbon particle to remove volatile organic compounds from an airstream is 4.55mm to 6.55mm. Smaller pieces tend to pack the filter bed causing dead air passages (blockages to the rest of us!) These cause extra airflow pressure on the live air passages.
Believe it or not, the hobby hydroponics industry has created some of the most advanced designs in carbon air filtration and these cutting-edge techniques to remove organic molecules from high flow airstreams has since spread to other industries. However, the basic shape of the filter has not changed since 1985 the cylindrical open mesh type canister, invented in Holland. It is by far the most popular shape in use today. There is no more efficient use of materials and space to filter organic molecules from high flow airstreams.
source: Urban Garden Magazine
