Do Misting Fans Really Work? What they don’t tell you!

Commercial misting fans are a popular addition for many events, agricultural and industrial spaces but how do they do in a patio type setting? Here I have covered all the different aspects from their water usage and usable range to climate suitability and how ‘wet’ you might get.

Misting fans can be very effective; the combination of cooling the air along with the benefits of a fan circulating it around. In ideal situations, it can drop the temperature by several degrees (more than 20F!) without getting you wet. The best models use the ‘Flash evaporation’ of tiny water droplets, which relies on the droplets being very very small!

Disclosure: There are affiliate links within this article, and at no extra cost, I earn a commission if you buy.

The best misting fans (like those at big sporting events, theme parks, etc) will produce a very fine (10 micron or smaller) droplet of water.

What they don’t say is that most residential systems will produce ‘some‘ very fine droplets but will also produce a lot of larger droplets!

These larger droplets do not ‘flash evaporate’ and can, therefore, end up just getting things wet. In many scenarios, this may still be OK (working outdoors, relaxing by the pool) and can even be a benefit (see below Forgotten Benefits to Misting Fans) but it can be very disappointing if you are planning to directly cool an Al Fresco patio dinner!

How Does A Misting Fan Work?

These systems combine a regular blowing fan with a water supply and a water pump. Water is pumped out of special misting nozzles, producing a fine spray, that goes into the air that is being blown by the fan.

You are then able to benefit from three forms of cooling:

  1. Conduction from your body to the cooler air. (Slight Benefit)
  2. Convection breeze from the fan (Moderate Benefit)
  3. Evaporation of the water making the air cooler (Major Benefit)

Of these, it is the evaporation of the water into the air that makes the largest difference. The process of water evaporating actually requires energy and it takes the heat energy out of the air to do it.

Evaporating 1 Gallon of water takes 8133 BTU’s of heat energy out of the air. That is the same as recommended for an A/C unit to cool a 400 sq foot room!

The key point is that the smaller the water droplets the faster they evaporate, the greater the cooling.

In an ideal system, the water droplets that create the mist are so small (10 microns or less) that they instantly flash-evaporate. That is to say, they evaporate instantly in the air before they fall to the ground. This both cools the air and ensures there is no water left to get you wet and without wetting the area to be cooled.

Its all about the water pressure!

All nozzles will give a range of sizes of water droplets, however, the finest mist ranges come from the smallest nozzle sizes.

The more expensive misting systems will have water pumps to increase the pressure of the water being pushed through the nozzles. It is this increased pressure that is required to push the water through the tiny holes required to make the fine water droplets.

Low Pressure20 – 120 psi
1 – 8 bar
Mains Water Pressure
e.g Garden Hose / Tap connections
Normally built with PVC or poly plastic tubing
Fine Spray
Finer than a sprinkler but will still get you wet.
$
Medium Pressure100 – 250 psi
7 – 17 bar
Basic Pump
Mist Spray
Mixed size of droplets
$$
High Pressure800 -1200 psi
55 – 83 bar
Specialist High Pressure PumpVery Fine / Fog spray
‘Flash Evaporation’
$$$$

The higher the pressure, the smaller the water drops, the better it is at cooling. But that isn’t the whole answer.

In most residential conditions a medium pressure system (see product suggestions below) will do a good job. It will have a pump to boost pressure from the tap or from a tank/reservoir. Ideally also having some control over water flow can help you tune the volume of water that collects before it evaporates.

It will not be a perfectly ‘dry‘ instantly evaporating mist/fog but it will cool the air that is blown.

To avoid getting wet at all is where the more expensive models really are required. To get the higher pressure (see product suggestion below) you need to use specialist materials (hose/pipes, nozzles, pump, etc) and you will need to filter the water. The nozzles are so small that any debris in the supply water will block them, causing at best frustration! Most nozzles clog because hard water deposits accumulate in the nozzle (like the white residue left on a shower door).

How Much Water do Misting Fans Use?

A standard portable patio Misting Fan will use between 1-2 Gallons an hour at full water flow.

To get the greatest amount of cooling you would ideally fill all the hot air with very fine water droplets that absorb lots of heat as they ‘flash evaporate’. In very hot and dry conditions (See below: Do Misting fans work in high humidity?) even the biggest commercial units can work at full water flow and still not get anything ‘wet’. They have special sensors to detect the temperature and humidity and adjust the water flow accordingly.

With the standard residential units, however, your decision is less likely to be affected by these factors. You will most likely have to adjust your water flow to a level at which you are satisfied with the amount of water build-up in front of the fan. Too much and you will end up having puddles, too little and you don’t get the full benefit.

So what About the Larger Water Drops?

Well, even the larger drops will still evaporate, they will just take longer to do so.

This is where you might end up getting wet and is where most residential misting fans sit in there capability. They spray some very fine droplets but also some larger droplets. Different manufacturers have different nozzle sizes, fan speeds, and water flow which gives them each a different result.

However, that doesn’t mean they are no good! Even with slightly larger droplets, that take a little bit longer to evaporate, it doesn’t mean you will get wet. It depends on how much control you have of the waterflow/pressure, fan speed, and how close you are.

If you have been sprayed briefly, even with slightly larger drops, you will feel the benefit as they evaporate. It is the same as when you rinse your face on a hot day and then feel the coolness as the water evaporates.

If, however, you remain next to a misting unit within range of the largest drops, then before the first drops can evaporate you will be getting soaked by the next!

Is Misting Fan Speed/Size important?

With a mist that doesn’t immediately ‘flash evaporate’ the smaller droplets have the potential to travel farther and will, therefore, have longer to evaporate. In other words, heavier water droplets will fall victim to gravity more quickly. This is another example of why a better quality fan with a higher percentage of very fine droplets is better.

The effective area that can be covered by any fan is a combination of fan blade size/pitch and its speed. A bigger fan can move slower and move the same amount of air.

It may seem obvious that, within reason, the faster the fan is running, the further away the effects of the cooled air can be blown. However, the fan will also be a lot noisier the faster it is running! This combination of factors may affect your choice of unit. A larger fan that can operate slower, maybe more suitable than a smaller unit running at full speed.

Most owners suggest that their fan at full speed is too noisy. Unless being used for cooling larger areas or sporting events, where the noise is less of a problem. In many cases having the fan a little further away to allow for a little water on the floor is less of a problem.

So How far Away is reasonable?

Even the best fans will still get you wet if you are within 4 – 6 feet or so of the nozzle, as the water droplets will not have been exposed to enough air to evaporate.

Otherwise, it seems from the reviews that if you are within 8-10 ft you may well get wet with many of the residential models.

Why Choose a Misting fan not just Misting?

The benefit of the fan for cooling makes a difference for two reasons:

Wind-chill effect

The standard benefit of any fan is the ‘wind-chill effect‘. It is the same effect that helps when you blow on hot food to cool it down. The movement of the air increases the loss of heat by convection. However, unless you are there to experience the wind chill then a fan is of no real benefit. All it does is circulate the hot air, it doesn’t actually cool it.

Tip: Most systems will let you use the fan on its own so you can choose how much cooling you want.

Tip: Turn off fans when you leave a room; fans cool people, not rooms, by creating a wind-chill effect.

Air Circulation when Misting

A much bigger benefit is the use of the fan when misting. The fan still circulates the air but now it is blowing the cooler air (created by the misting) away to be enjoyed.

It is also drawing in new hot air that is less humid. This means that the evaporation process can occur easily as the new air is not saturated (high humidity).

Tip: Unlike just using a fan, when using a misting fan, leaving it on even when you are not there, will significantly cool the surrounding environment.

Do misting fans work in high humidity?

Yes, they can but you can only use a smaller amount of mist before the air is saturated. Only using a small amount of mist also means you only get a smaller reduction in temperature. But you can still get some cooling.

You, therefore, need to ensure that the water droplets are as small as possible to get the most efficient cooling of the air being blown. This requires the higher water pressure systems.

> 80% HumidityMax ~ 10 degrees F of cooling
40-80% HumidityUp to 20 degrees F of cooling
< 40% HumidityOver 30 degrees F of cooling
Results in ideal measured conditions.

Cooling of air by evaporation can only occur if the air is unsaturated. i.e the humidity of the air is less than 100%. As the humidity level drops it means there is more space in the air for water to evaporate. The more water that evaporates the cooler the air will be.

It follows that areas with lower relative humidity (think the dry, hot climates such as the west coast of the USA) can add more water to each volume of air before it is saturated. These areas can, therefore, experience a greater cooling effect than areas with high humidity.

Indications for evaporative cooling use around the world (from coolmax)

This map was elaborated in great scale and it does not reflect the local microclimates.

Forgotten benefits to using Misting Fans

  • Cleaner Air: In many commercial settings (mines, building sites etc) mist cannons are used to help suppress dust and other contaminants, even air pollution and Smog! Those fine water droplets that do not instantly evaporate will collide with particles in the air and fall to the floor with them.
  • Cooler Environment:Misting fans cool the air and therefore can help cool the surrounding environment even when you are not there! Unlike a fan, turning it on in preparation for your arrival can make the area more comfortable before you arrive.
  • Bugs; As much as the mist keeps down pollution it is also keeping the flying insects away!
  • Cost; So maybe not a forgotten benefit but certainly worth remembering as the cost to run is very efficient

Disclosure: There are affiliate links within this article, and at no extra cost, I earn a commission if you buy.

Product Suggestions:

Low / Medium Pressure Models

NewAir, AF-520B, Outdoor Misting Oscillating Pedestal Fan

18″ Fan size, 3 Speed

Many people recommend the addition of finer nozzles and a filter to improve further the misting of this fan. Orbit 10106H Misting Nozzle. Orbit 10109W Mist Calcium Inhibitor Filter

Pros: This unit comes with some built in safety features for the electrics and also has a waterflow valve that can be adjusted to limit the water if you are getting too wet.

Cons: Given that it is designed to spray water some comments about showing signs of rust after the first year.

Lasko 7050 Misto Outdoor Misting Fan 

Portable Misting Fan but still needs hose and power connection.

Cool-Off 12 Gallon Island Breeze Oscillating Misting Fan with 3-SPEED QUIET OPERATION

Pros: Large Fan Size (26″) means it can run slower (quieter!) but still move a lot of air. It also has adjustable waterflow and built-in overload protection. Outdoor rated fan so has higher quality more robust components.

Cons: Quite a large unit

Note: This uses there own centrifugal misting system rather than nozzles.

High-Pressure Fan Misting Systems 1000PSI

HydroMist R-S-1-18-5B 18″ One Misting Fan Package, 1000 psi, Black

This professional-level system can be expanded to include other fans or even to add further nozzles to create a patio style misting system.

These high-pressure systems will create the finest mist that will give the greatest amount of cooling without getting you wet.