1. Diffusing CBD Oil
2. What is Diffusion?
3. How Diffusion Works
4. Popular Means of Diffusing Oils
4.1 Evaporative Diffusers
4.2 Heat Diffusers
4.3 Ultrasonic Diffusers
4.4 Nebulizing Diffusers
4.4.1 What is Bioavailability and Why Does It Matter?
5. Can Any CBD Oil Be Used in a Nebulizer?
6. CBD Nebulizer for Lung Diseases—a Possibility?
7. CBD for Insomnia and Anxiety
Diffusing CBD Oil
Cannabidiol (CBD), a derivative of the Cannabis sativa L. plant, is known for its many excellent healing properties and health benefits. Currently, in the U.S., CBD is sold in various preparations or forms and is growing in popularity following hemp's legalization late in 2018.
However, it's also common knowledge that the market is not yet regulated properly. This means that the thousands of CBD products for sale are not standardized at all, and thousands of users have to rely on experimentation to find a product that works for them.
One lesser-known way to ingest CBD is via diffusion. Users get extremely good results and prefer this to any other method of administration. It has great value and can potentially become even more popular than tinctures over time.
However, don't make the mistake of buying the common CBD diffusers on the market. Read on for more.
We did some research to find out what works and why.
Let's start by getting the definitions straight.
What Is Diffusion?
Diffundere is the Latin root of the word "diffusion," and it means "to spread out."
A common example of diffusion would be the distribution of a spoonful of sugar in a cup of hot tea. First, it dissolves, and then it spreads through the liquid.
Or, think of the scent of essential oil or perfume spreading through the air in a room. For the latter, there are hundreds of devices on the market.
Many users have wondered whether CBD can be distributed in the same way as a means of administration. Can the oil be diffused, for instance, in a child's room so as to promote sleep and tranquility? And what about the previously mentioned CBD diffusers on the market?
While inexpensive and disposable, these are completely unlikely to have any result other than leaving a faint smell of cannabis in your house. These have absolutely no value in terms of health benefits. This is due to the cannabinoid's molecular nature.
How Diffusion Works
In chemistry, the process of diffusion is defined as: 
...the movement of a fluid from an area of higher concentration to an area of lower concentration. Diffusion is a result of the kinetic properties of particles of matter. The particles will mix until they are evenly distributed. Diffusion may also be thought of as the movement of particles down a concentration gradient.
So, in essence, diffusion is a process whereby molecules are transported from one area to another. In the diffusers under discussion, these particles are set in motion with the application of heat (thermal) energy. They move about randomly, and after a while, this random movement leads to a uniform distribution of the different particles. Increased temperature or pressure will increase the rate of diffusion. 
This long-ish explanation is necessary to illustrate an important point about CBD diffusion—it’s all about the molecules. And since CBD is a large, oil-soluble molecule, the manner of diffusion matters.
Popular Means of Oil Diffusion
As mentioned, diffusers are popularly used to spread aromatic essential oils in the air—not only for their fragrance but also as a means to confer their health properties. The devices include heat and steam diffusers, but these won't work for oil-based products. We know that CBD is oil-soluble and therefore a so-called hydrophobic molecule, so any water-based diffuser won't disperse the cannabinoid's particles at all.
Oil delivery devices include the following:
1. Evaporative Diffusers
Here, the oil is dropped onto a permeable pad in the diffuser so it can evaporate into the air. Some have fans to encourage the process. This is the most affordable and simplest method of diffusion, but not enough CBD will be dispersed this way to have any effect on your body. This is suitable only if you're looking to distribute its scent.
2. Heat Diffusers
Also simple and cost-effective, this method adds heat to the evaporation process. These devices involve the flame of a candle heating a pool of oil, which will cause the oil's scent to disperse into the air.
The problem with this method is the same as the previous one—the CBD in the air will have virtually no value for your health or well-being. Candles could also be a problem in spaces where open flames are prohibited.
3. Ultrasonic Diffusers
This is the most popular diffuser for essential oils in particular.
As the experts explain: 
An ultrasonic diffuser is an aromatherapy diffuser that uses electricity to disperse essential oils into the air. They break the essential oil particles down into their base molecules. These molecules are negatively charged so they disperse by attaching the positively charged molecules in your home. Ultrasonic diffusers use water as a transference mechanism but do not rely on steam. Instead the oil sits on top of the water and ultrasonic vibrations are created to agitate the water causing the separation of the oil molecules and releasing the negative particles into the air with a fine mist.
Ultrasonic diffusion has one major drawback: it dilutes the oil molecules considerably with water. This means that you won't even smell the CBD very strongly. Again, it's completely unlikely to cause calmness, stress relief, and sleep.
Other cons are that the water in the tank of the device can encourage mold and fungi to grow. Many devices are also not of very good quality, which means that they're not durable.
NB: These ultrasonic diffusers shouldn't be confused with another type, however. Some medicines for chronic obstructive pulmonary diseases (COPD) used to be packaged in handheld devices that worked with electricity, called ultrasonic nebulizers. They are also referred to as inhalers and "cool mist devices." These are outdated mechanisms for administering medicines and are almost completely out of use today.
If you're looking to tap into CBD's health benefits in diffused form, then a nebulizer could be what you're looking for.
4. Nebulizing Diffusers
Some call this the future of CBD administration, as nebulizing is a particularly clean and effective way to dose.
A nebulizer device works like a perfume atomizer, and its functioning is very simple, as explained by Alexandra Hicks, writing for CBD Testers: 
The jet in the nebulizer pushes compressed air through rubber tubing filled with CBD oil. Air moves at an extremely high velocity through the oil, turning it into a clean aerosol spray that flows through tubing to be inhaled by the patient.
She goes on to mention that medical professionals and hospitals across the globe will attest to the benefits of using a nebulizer to administer medications. "The effects of nebulized CBD will be much purer. Plus, since it becomes an aerosol, there is no residue or lingering odor that remains after use."
Dr. Jordan Tishler, a Harvard-trained physician, cannabis therapeutics specialist, and president of the Association of Cannabis Specialists and CEO at inhaleMD, spoke to The Growth Op about cannabis nebulizers and their advantages. 
Nebulizing is the only pulmonary delivery method that doesn’t require heating or combustion of the cannabis product. And unlike edibles, dosage can be controlled, too, which is especially beneficial for those using cannabis medically.
CBD emulsions have furthermore demonstrated a much higher bioavailability compared with other forms of delivery. This is because almost none of the compound is lost during physiological processes such as metabolization and/or digestion.
What is Bioavailability and Why Does It Matter?
Basically, bioavailability is the percentage of any active compound that eventually gets absorbed and utilized by the body. Many see this as a criterion for clinical efficacy, even though testing a substance's rate of absorption is somewhat problematic. 
Different means of administration affect a product's bioavailability. For instance, intravenous administration of CBD would make it 100 percent bioavailable, while a CBD capsule's bioavailability is much lower due to metabolization, digestion, etc. (In other words, the substance has to go through many processes in the body before it reaches the site of therapeutic activity.)
It's good news—it means that with nebulizing CBD, you will feel the effect of the product much faster. You will also get much more for your buck because your body will use almost all the CBD you take. Users attest that they use a lot less of the product this way, so it's cost-effective too.
This is an important consideration because a good, high-quality nebulizer is expensive. However, in the long run, you could save money because your CBD will work better than ever (decreasing the need for other medications, perhaps) and you won't have to take a high volume of the product to feel an effect.
Not that nebulizing CBD is without challenges.
Can Any CBD Oil Be Used in a Nebulizer?
In short—no. The challenge with cannabis products in diffusers, as described earlier, is that the device still uses water, and we know that all cannabinoids are hydrophobic.
Nebulizers are mechanically superior to other diffusers, but they still work with water. This means that putting a basic cannabinoid extract in it will still not deliver the remedy effectively because water and oil don't mix well.
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However, science has found ways around this limitation. Yaron Eshel, director of life sciences for iCAN: Israel-Cannabis explains:
There’s a whole industry now looking at water solubilization technology ... So how do I get this oil and make it into very small molecules so that the body can absorb it? It’s called nanoencapsulation. It’s very standardized in the drug industry, very standardized in the food industry.
Eshel believes that nebulization is one of the most effective forms of pulmonary delivery that doesn’t involve heat.
So, nanoencapsulation seems to be the answer. Some early adopters have already started to manufacture CBD nebulizers with properly formulated oil.
Yet more research and more refining of the science are necessary before CBD nebulizers are likely to hit the market. The hope is that this particular product will be more standardized and consistent, so the dangers associated with low-quality vape pens, for instance (another very popular pulmonary delivery system for CBD), can be avoided from the onset. This way, nebulizers will have a clear advantage over vaping, which is controversial, to say the least.
CBD Nebulizer for Lung Diseases—a Possibility?
As was touched upon earlier—this method of administration will be of particular advantage to COPD patients.
Traditionally, tetrahydrocannabinol (THC) is associated with beneficial effects on the lungs as a bronchodilator in particular. However, its mind-altering properties make it an unpopular choice for therapeutic study and use.
Enter CBD, THC's cannabinoid cousin, which studies show also demonstrates a utility to treat airway disorders.
One study investigated the effects of CBD for its actions on the bronchial smooth muscle in both the lab as well as in animal subjects. 
In conclusion, our results suggest that cannabidiol can influence antigen-induced airway smooth muscle tone suggesting that this molecule may have beneficial effects in the treatment of obstructive airway disorders.
Another earlier study demonstrated CBD's anti-inflammatory effects in mice with acute lung injury. 
CBD for Insomnia and Anxiety
Anecdotally, CBD seems to soothe common conditions such as sleeplessness, restlessness, and anxiety.
Science supports these notions, even though a lot more clinical research is required. One recent review of the literature on cannabis and sleep reports: 
Preliminary research into cannabis and insomnia suggests that cannabidiol (CBD) may have therapeutic potential for the treatment of insomnia. Delta-9 tetrahydrocannabinol (THC) may decrease sleep latency but could impair sleep quality long-term. Novel studies investigating cannabinoids and obstructive sleep apnea suggest that synthetic cannabinoids such as nabilone and dronabinol may have short-term benefit for sleep apnea due to their modulatory effects on serotonin-mediated apneas. CBD may hold promise for REM sleep behavior disorder and excessive daytime sleepiness, while nabilone may reduce nightmares associated with PTSD and may improve sleep among patients with chronic pain. Research on cannabis and sleep is in its infancy and has yielded mixed results. Additional controlled and longitudinal research is critical to advance our understanding of research and clinical implications.
CBD might not cure insomnia, but it could be a very effective sleeping aid.
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CBD's effects on anxiety compared to THC's could be more pronounced, as demonstrated in one observational study of 15 human subjects: 
Delta9-Tetrahydrocannabinol and CBD had clearly distinct effects on the neural, electrodermal, and symptomatic response to fearful faces. The effects of CBD on activation in limbic and paralimbic regions may contribute to its ability to reduce autonomic arousal and subjective anxiety, whereas the anxiogenic effects of Delta9-THC may be related to effects in other brain regions.
While THC seemed to cause anxiety, CBD's effects were just the opposite. Imagine a fast-acting CBD nebulizer and what it could do for sufferers of PTSD, acute anxiety, anxiety attacks, and so forth.
With nebulizing diffusers, the market is perhaps poised to explode once again...