s/inhalers/nebulizers/ See, e.g., https://www.ncbi.nlm.nih.gov/pubmed/12425745 https://www.ncbi.nlm.nih.gov/pubmed/12425745 It's also listed as approved as an

s/inhalers/nebulizers/ See, e.g., https://www.ncbi.nlm.nih.gov/pubmed/12425745 https://www.ncbi.nlm.nih.gov/pubmed/12425745 It's also listed as approved as an inactive ingredient by the FDA, including for inhalation: PROPYLENE GLYCOL | RESPIRATORY (INHALATION) | LIQUID | 57556 | 6DC9Q167V3 | 10%w/w PROPYLENE GLYCOL | RESPIRATORY (INHALATION) | SOLUTION | 57556 | 6DC9Q167V3 | 25%w/w Source: https://www.accessdata.fda.gov/scripts/cder/iig/index.cfm?event=browseByLetter.page&Letter=P https://www.accessdata.fda.gov/scripts/cder/iig/index.cfm?ev..., page 39.