So nebulizing vitamin C turns out to be really easy. You just dissolve a couple grams of AA (ascorbic acid powder) or SA (sodium ascorbate powder) in, say, 2 tablespoons of distilled water. SA dissolves more easily. Put some of that in the cup of your compressor nebulizer, we use a Pari Trek. Nebulize away. AA tastes tangy when you're nebulizing it. SA is pretty neutral. AA is likely a little more effective, but SA works just fine.
Nebulizing vitamin C delivers it directly to the lungs. Transport of ascorbate in the body is not necessarily easy. The lungs can use a lot especially if there is a viral or bacterial infection underway. Direct distribution to the bronchi will clear the lungs rapidly and can shut down asthmatic spasms.
Taking oral doses of vitamin C to bowel tolerance is always the first step to shut down disease symptoms, so even when nebulizing you should be taking large oral doses to get your internal level of ascorbate high. Nebulizing then tops off the level at the lungs. Along with large, bowel tolerance doses of vitamin C, nebulizing may be helpful for:
viral pneumonia or a severe cold (like that cold/flu they're calling "COVID").
anaphylaxis due to an allergic reaction (insect sting, food allergy, pet allergy, etc.).
concussion and trauma.
COPD, asthma, and other breathing issues.
lung cancer or other cancer's or disease of the chest, head, neck.