Carbon filters have been used for hundreds of years and they are one of the oldest methods used for purifying water. Evidence has shown that carbon filtration may have been used in ancient Egyptian cultures for sanitizing both air and water as far back as 2000 BC.

These filters are widely used in hydroponics to eliminate airborne smells associated with indoor growing. Extracted air from a grow room is often pungent and easily extracted with the use of a carbon filter. Typically, these filters are suspended from the ceiling and then attached to the intake of an extractor fan. Air is drawn through the filter before it is extracted outside. Air purification is a critical element for a healthy grow room and carbon filters should be used whenever it is possible to ensure the best results.

The two predominant types of carbon filters are block filters and granular filters. Block carbon filters are typically used for larger crops, as the increased surface area of the carbon makes these more effective at removing a larger numbers of contaminants. Granular filters, which are ideal for personal hydroponic crops, contain granules of activated carbon which filter and absorb unwanted smells and air contaminants as the expelled air passes through. In addition, a simple setup of an extraction fan and ducting will allow fresh air to be replenished in the grow room.

It was discovered in the 19th century that plants absorb their essential nutrients as inorganic ions in water. Soil is not essential to plant growth; the soil simply acts as a nutrient reservoir. It is only once the nutrients in the soil are dissolved in water, that plants are then able to absorb them. Almost any terrestrial plant will grow using hydroponics as long as the required nutrients are artificially added to its water supply.