Aeroponic Mister vs Fogger: What’s the Difference?

This is for those of you who are looking to develop their aerogarden. As most of you might know, plants in aerogardens receive their nutrients from tiny water droplets. These tiny water droplets are usually created using misters or foggers. While there is a difference between the two, they serve similar functions in your aerogarden. In order to successfully harvest plants from an aerogarden, the enclosure containing them must have a balance between the air temperature and humidity. Too much moisture can result in high levels of humidity which risks the onset of fungi, moss, grey mold, and fungus gnats which are adverse to the growth of plants and also means higher maintenance works. However, the lack of moisture spells trouble when the air temperature is too high, causing leaf temperature to increase. In these cases, the plant might lose water faster than it can intake it which builds up stress in the plant. So, a mister and fogger can easily solve these issues as the tiny water droplets mean that there will be little moisture remaining in the environment whilst the area is kept cool enough.

The differences between mister and fogger

Equipment used to produce mister versus fogger

Compared to the latter, the mister contains filters, piping, nozzles, a pressure regulator, a solenoid valve, and a controller or timer. Whereas, the fogger is made up of a high-pressure pump, distribution piping, and nozzles. As such, mist systems typically operate at 30-60 psi water pressure to produce water droplets of size 50 microns and larger. Then, the fogger systems experience higher water pressures at 800 to 1200 psi which create water droplets 10 to 20 microns in size. Hence, foggers tend to produce tinier sizes of water droplets which means less moisture than the typical mister.

Various instruments hanging on wooden board in garage

Operation differences between mister versus fogger

Let us first talk about the mister. A solenoid valve has to be in place to serve as the main control for turning the water off and on. The valve should be easily operable with a snap action and utilize the same voltage as the controller or time clock. It is recommended to get those that operate on a 24-volt system. Misters can be controlled with timers so that the system works in intervals to evenly distribute the water. The timer can control the interval like turning on the system for 3 seconds after every three minutes for example. 

There will also be other equipment in place like a mechanical sensor that gauges if there is excessive moisture in the environment. When the sensor detects that, it will trigger the solenoid valve to turn off the water system. So, this will help to ensure that your plants will not be receiving too much water. This is especially helpful for weather changes as it will adjust accordingly depending on the day being cloudy or sunny. There are also other tools like light-operated interval switch (LOIS) and a humidistat that cover other aspects. For the former, the solenoid valve will be activated more frequently on a sunnier day where the LOIS receives more sunlight. The latter will monitor the humidity in the environment to ensure that the appropriate humidity level is maintained.

Now, for the foggers, they can either be operated using the standard equipment mentioned above or high-speed fans with water channeled to the tip of the blades. For the standard equipment, they are operated with a controller or computer. These devices are used to gauge the vapor pressure deficit (VPD). The VPD serves the function of indicating when the balance between a plant losing water and the rate of intaking water is mismatched. As mentioned above, this would result in plants becoming highly stressful within. So, the VPD signals to you when there is a danger of that occurring and makes the necessary changes to the fogging system to ensure that plants are well managed. The nozzles should also have anti-drip check valves to minimize leakages from happening when the system is turned off. Furthermore, as foggers have more layers than misters, they are more prone to having mineral deposits clogging up the nozzle. This is where the high-speed fans come in to eradicate this problem. As the fans are moving at high speeds, the water that is channeled out through the blades goes through a shearing action which reduces the water flow to fine droplets and thus, produces fog. 

This system is slightly more advantageous due to the fact that it sidesteps the problem of having minerals clog the nozzles since it does not use nozzles at all. However, many have feedback that this system in turn generates a high volume of noise. Hence, there are typically two ways that foggers can operate, both with their own pros and cons.

Thus, the differences between misters and foggers lie in their different operations systems and the different measurements used to gauge environmental changes.

Field of Plants in Greenhouse

Placement for misters vs foggers

In this case, there is little difference between the two systems. The mister can have two placement spots, either supported above the bench on risers or suspended from cables that hang at the ceiling. These devices are usually placed 3ft to 5ft above the crop so that there can be better coverage over them. As for the fogger, they are typically only placed above the crop area to ensure that there is an even spread over the crops as well. Hence, the difference lies in that the mist system has a more flexible installation depending on the type and needs of your crops.

Hence, the type of system to use ultimately depends on what you want for your aerogarden. The mister system is more common and less complex for personal aerogardens. Whereas, for those on a larger scale looking to get into the markets, the fogger system is the more recommended option. So, the important thing would be to first establish your own goals before you set up the respective systems for your aerogarden.

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