Searching for the best home or office aroma diffuser? You type "aroma diffuser" or similar into your browser search bar and wham! Instant overwhelm!

What’s the difference? Why do some cost more? Are they safe for my family and friends?

Many diffusers look exactly the same on the outside, but on the inside, they are completely different. Consider the photo below. The diffuser on the left is a nebulizing diffuser that emits pure essential oil in bursts. The other is a humidifier and vibrates water to put out fog that you drip scent into. They couldn't be more different, but how would you know that by looking at them?

Left: An essential oil nebulizing diffuser. Right: An ultrasonic vapoizer that emits mostly water.

The shopping sites I visited offered little help. I did four searches on a well known site. I searched “waterless scent diffuser” and “nebulizing aroma diffuser” and “best scent diffuser” and "essential oil diffuser". All four searches returned the very same diffuser selection - only varying the order! And worse yet, every diffuser that appeared used water - even though I had typed "water free" and "waterless" as search terms. Geez!

I’m a diffuser expert! How would a non-professional know what they were seeing?!

Fortunately help is here! We’ve been building and providing diffusers to hotels, businesses, aquariums and even hospitals since 2005. So here's your quick expert guide about the types of aroma diffusers with pros and cons of each.

There are 5 common types of electronic aroma diffusers for home and office use. They are:

Ultrasonic vaporizers - the most common - are not really diffusers. They are humidifiers. Tell tale sign: They require water.

Evaporators - are the type that you drip your scent oil onto a plate or ring and it evaporates with heat. Tell tell sign: A heated plate.

Fan diffusers - have a fan that blows over gel or a scented pad. Tell tale sign: You guessed it...a fan.

Vacuum diffusers - the kind with the glass bulb and tiny tubes inside it. Tell tale sign: Glass and a loud buzz Spicoli.

Nebulizing diffusers - have a pump that and emits aroma from the top in bursts of mist. Tell tale sign: timed bursts of very fine mist.

Let's quickly examine the benefits and drawbacks to each.

Ultrasonic vaporizing diffusers or UVDs: First the good. They are cheap! They can be quite attractive. They are quiet. They are easy to use: Fill with water and add a few drops of your favorite scent. Turn it on and a cool fog pours out with a bit of your aroma in it. The bad? Mold. Consumer Reports says that every UVD they tested grew and emitted mold. Even those marked as "germ free" and "anti-bacterial." Consumer Reports said you have to clean them daily and let them dry completely before refilling. And a few drops of essential oil will NOT be enough to sanitize the water. Water and essential oils don't mix - they separate. So what you see coming out is not aroma - it's 99.9% water vapor - with a tiny bit or aroma.

"Every ultrasonic diffuser Consumer Reports tested grew and emitted mold"

Bottom line: Too much work for me. Lots of cleaning and drying. Little scent. I don't need humidity and mold in my space.

Evaporating style diffusers: These include reed diffusers and the type with porous stones or shells on a heating plate. They are quiet and they can scent a very small space like a bathroom. I like how they look. The drawbacks are that reeds are not super effective if you want essential oils. And the plates - due to the aroma or essential oil poured on the rocks - will get dust stuck to them. If you are willing to clean the rocks are shells weekly, they are a good diffusers for small spaces.

Bottom line: Lots of cleaning. Little scent.

Fan Driven Diffusers: This type of diffuser can be very effective if the fan is powerful. Small units can scent a car or bath. Here's what we hear from clients that use them: Whether battery driven or plug in, fans use a lot of energy - batteries or AC. They are probably the loudest type of diffuser. But there is more important problem: You can't regulate the scent. Whether the unit blows over a chemical cartridge or has a pad you drip the scent onto, either way, it's potent to start out and diminishes in potency each hour, day, week. How do you regulate that?

Bottom line: Loud. Not energy efficient. Tough to regulate scent.

Vacuum Style Diffusers: This type has a glass bulb with tiny glass tubes inside it. They usually have an LED light that changes color. They can have a wood base or a high tech exterior with the glass hidden inside. I think they're kinda cool, retro looking - like a lava lamp. The downside is the glass is fragile. And the tiny tubes inside always become clogged. When that happens, the rubber bladder in the aquarium pump gives out. Game over. Then you hear the loud pump buzz, but no scent comes out. If you have one, I bet this sounds familiar!

Bottom line: Loud. Fragile. Lots of cleaning and soaking.

Nebulizing diffusers do not use water. They use a high powered pump to micronize the scent.

In my opinion, the best diffusers for the price are nebulizing diffusers. They work with a powerful pump that causes the liquid aroma to micronize into particles of 1 or 2 microns in size (about 50 to 100 times smaller than aerosol). The tiny particles become scented air. They travel a long way. They don't float down and coat floors and furniture. Nebulizers can be small and affordable or super powerful. Some scent up to 2500 square feet! They don't use water - so no mold! 100% of the emitted aroma is pure scent. And every burst produces the same scent strength level from the first day to the bottom of the bottle.

They are ideal for pure essential oils, which are anti-bacterial, anti-fungal, anti-viral and anti-microbial. So you are actually cleaning bacteria, fungus, mold, microbes and many viruses from the air! Hospitals are saying that unlike synthetic anti-germ scent and disinfectants, essential oils are highly complex and effective at killing stubborn germs like MRSA!

Most nebulizing diffusers have programmable daily on and off settings, as well as burst and rest periods. They can be easily adjusted for the size of the space and cost only pennies per day to run. Set it and forget it until you refill. If it’s a good machine, it will last for years. Some you can even control with your phone.

Are there any downsides? Well, it depends on your point of view. They are usually a little more expensive. Prices range from as little as $69 to as much as $325 for all the bells and whistles. Once you have the scent in them, you must keep them upright or the liquid will pour out the top. Oh and I should mention, they make a little noise only when the scent is emitted - about the level of a whisper (15dB) on a good machine – a little louder on cheaper models. But that’s something to consider if you will use it when sleeping if you are a very light sleeper. It doesn’t bother most people, but consider that when locating it.

One important tip is to only use the essential oil and blends recommended by the manufacturer. Many blends will clog your diffuser and require service and may void its warranty. I've had this happen even with some I thought were reputable EOs.

So there you have it! An insider's guide to diffusers. I look forward to questions and coments. I hope you found this info helpful so you can find the best diffuser for you! Thanks for reading! And be sure to check out our other blogs.