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Glycol Vapors Explained: What They Are and What We Know So Far
A Q&A on the current evidence, potential applications, and questions that remain
08/25/26
Glycol vapors for treatment against airborne pathogens have been studied since the early 1940s, after researchers identified their antimicrobial properties and explored their potential to reduce disease transmission. Despite this early interest, the intervention remained largely underexplored for decades before reemerging as a potential air treatment technology of interest amid and following the COVID-19 pandemic. While glycol vapors may be a promising intervention, important questions remain about their safety, efficacy, and potential use in occupied indoor spaces.
Below are answers to common questions about glycol vapors, the current state of the evidence, and how Blueprint Biosecurity is approaching this emerging area of research.
Q: What are glycol vapors?
A: Glycols are a group of compounds used in a range of food, cosmetic, pharmaceutical, entertainment, and industrial applications. When dispersed into the air in vapor form, some glycols possess antimicrobial properties. The glycols that Blueprint is evaluating as potential airborne pathogen interventions are propylene glycol (PG), dipropylene glycol (DPG), and triethylene glycol (TEG). These compounds may be found in theatrical fog, food additives or food packaging materials, fragrances, and other personal care products.1–4
Q: Why did Blueprint choose to focus its work on propylene (PG), dipropylene (DPG), and triethylene (TEG) glycols?
A: Blueprint is evaluating PG, DPG, and TEG given their antimicrobial activity in the vapor phase2,5–8, low toxicity1,9,10 (as observed by the U.S. Environmental Protection Agency), and potential for rapid deployment at the onset of a pandemic involving an airborne pathogen. These qualities make them an interesting intervention to better understand and explore as a potentially safe and effective air treatment technology.
Q: How do glycol vapors differ from other air treatment technologies?
A: Established environmental control and air treatment technologies such as outdoor air ventilation, filtration, and upper-room germicidal ultraviolet irradiation are well studied and have demonstrated efficacy in reducing infectious airborne pathogen concentrations.11,12 However, deploying these interventions rapidly and at scale during an emergency remains challenging. PG, DPG, and/or TEG vapors may have the potential to be used as a rapidly deployable emergency countermeasure given their substantial existing production volume and possible generation via widely available dispersion devices.5,6,13
Q: How are glycol vapors thought to inactivate infectious airborne pathogens?
A: Glycol vapors can condense onto, or partition into, bioaerosols.14 When present at high enough concentrations, the glycol vapors are then hypothesized to facilitate microbial inactivation through dehydration, protein denaturation, and/or membrane disruption.2,15,16
Q: What kind of infectious pathogens can certain glycol vapors inactivate?
A: Research to date indicates that glycol vapors have facilitated effective inactivation of diverse microbial organisms, including viruses, bacteria, and fungal spores,5,7,17,18 as well as known human pathogens like SARS-CoV-2.2,16
Q: Are the glycol vapors Blueprint is evaluating safe to inhale?
A: Concentrations of PG, DPG, and TEG glycol vapors capable of inactivating airborne pathogens5,7,8,17 are unlikely to cause substantial adverse effects.9,10,19 However, certain reactions, including mild skin drying and eye irritation, may be possible.1,20–22 While the available evidence is promising, additional research is needed to understand the effects of deploying glycol vapors in occupied indoor spaces among diverse populations. Blueprint is working to address these concerns by funding relevant studies, including the evaluation of inhaled glycol vapors among people living with asthma. See our GlycolISER Award Recipients press release for more details.
Q: How might glycol vapors interact with filtration systems or filter media?
A: This remains an open question that Blueprint is actively funding research to understand. See our GlycolISER Award Recipients press release for more details.
Q: What types of indoor spaces could be most appropriate for glycol vapor use?
A: Blueprint’s current understanding is that glycol vapors may be most useful for deployment in spaces that have difficulty meeting ASHRAE 241 standards with commonly available air treatment technologies during a pandemic or other public health emergency involving an airborne pathogen. Glycol vapors may be most effective in spaces that generally maintain intermediate temperatures and relative humidities, given that these compounds have demonstrated rapid inactivation efficacy under such conditions.5,8,23,24 These conditions also overlap with those recommended for human comfort and safety.25,26
Q: What are the most important gaps in the current evidence base?
A: The need for further evaluation spans questions around inactivation efficacy, transmission suppression, safe exposure, and practical deployment. Among the most critical gaps in the research are the elucidation of the relative contribution of inactivation mechanisms, airborne transmission suppression evaluations in modern indoor environments and across varying proximities of airborne transmission, and long-term exposure assessments in humans. Another area of interest includes exposure assessments among potentially sensitive populations.
In relation to rapid emergency deployment at the onset of an outbreak, it will be important to understand achievable glycol vapor concentrations, stability, and resulting pathogen inactivation from glycol vapors dispersed via non-purpose-built devices. Additionally, questions about potential degradation byproduct generation from such non-purpose-built devices, as well as solutions following long-term glycol storage, remain. Interactions of glycol vapors with other air treatment technologies and building systems still need to be delineated to inform practical deployment considerations.
References
1. Dalton, P., Soreth, B., Maute, C., Novaleski, C. & Banton, M. Lack of respiratory and ocular effects following acute propylene glycol exposure in healthy humans. Inhal. Toxicol. 30, 124–132 (2018).
2. Duggan, K., Ijaz, M. K., McKinney, J. & Maillard, J.-Y. Reviewing the evidence of antimicrobial activity of glycols. J. Appl. Microbiol. 135, (2024).
3. Fowles, J. R., Banton, M. I. & Pottenger, L. H. A toxicological review of the propylene glycols. Crit. Rev. Toxicol. 43, 363–390 (2013).
4. Fiume, M. M. et al. Safety assessment of propylene glycol, tripropylene glycol, and PPGs as used in cosmetics. Int. J. Toxicol. 31, 245S–60S (2012).
5. Sultan, Z. et al. Effectiveness of triethylene glycol disinfection on airborne MS2 bacteriophage under diverse building operational parameters. Indoor Environments 1, 100042 (2024).
6. Ratliff, K. M. et al. Impact of test methodology on the efficacy of triethylene glycol (Grignard Pure) against bacteriophage MS2. Aerosol Sci. Technol. 57, 1178–1185 (2023).
7. Gomez, O. et al. Airborne murine coronavirus response to low levels of hypochlorous acid, hydrogen peroxide and glycol vapors. Aerosol Sci. Technol. 56, 1047–1057 (2022).
8. Puck, T. T., Robertson, O. H. & Lemon, H. M. The bactericidal action of propylene glycol vapor on microorganisms suspended in air: ii. The influence of various factors on the activity of the vapor. J. Exp. Med. 78, 387–406 (1943).
9. U.S. Environmental Protection Agency. Reregistration Eligibility Decision (RED) For Triethylene Glycol. (2003).
10. U.S. Environmental Protection Agency. Reregistration Eligibility Decision For Propylene Glycol and Dipropylene Glycol. (2006).
11. Reed, N. G. The history of ultraviolet germicidal irradiation for air disinfection. Public Health Rep. 125, 15–27 (2010).
12. Morawska, L. et al. How can airborne transmission of COVID-19 indoors be minimised? Environ. Int. 142, 105832 (2020).
13. The Personnel of Naval Laboratory Research Unit No. 1. A simplified propylene glycol dispenser for field use. Science 97, 208–208 (1943).
14. Puck, T. T. The mechanism of aerial disinfection by glycols and other chemical agents: II. An analysis of the factors governing the efficiency of chemical disinfection of the air. J. Exp. Med. 85, 741–757 (1947).
15. Hirama, Y. et al. Antiviral effect of propylene glycol against envelope viruses in spray and volatilized forms. Viruses 15, (2023).
16. Styles, C. T. et al. Propylene glycol inactivates respiratory viruses and prevents airborne transmission. EMBO Mol. Med. 15, e17932 (2023).
17. Robertson, O. H., Bigg, E., Puck, T. T., Miller, B. F. & Technical Assistance of Elizabeth A. Appell. The bactericidal action of propylene glycol vapor on microorganisms suspended in air. I. J. Exp. Med. 75, 593–610 (1942).
18. Mellody, M. & Bigg, E. The Fungicidal Action of Triethylene Glycol. J. Infect. Dis. 79, 45–56 (1946).
19. Werley, M. S. et al. Non-clinical safety and pharmacokinetic evaluations of propylene glycol aerosol in Sprague-Dawley rats and Beagle dogs. Toxicology 287, 76–90 (2011).
20. Ballantyne, B., Snellings, W. M. & Norris, J. C. Respiratory peripheral chemosensory irritation, acute and repeated exposure toxicity studies with aerosols of triethylene glycol. J. Appl. Toxicol. 26, 387–396 (2006).
21. Wieslander, G., Norbäck, D. & Lindgren, T. Experimental exposure to propylene glycol mist in aviation emergency training: acute ocular and respiratory effects. Occup. Environ. Med. 58, 649–655 (2001).
22. Robertson, O. H. et al. Tests for the chronic toxicity of propylene glycol and triethylene glycol on monkeys and rats by vapor inhalation and oral administration. J. Pharmacol. Exp. Ther. 91, 52–76 (1947).
23. DeOme, K. B. The Effect of Temperature, Humidity, and Glycol Vapor on the Viability of Air-Borne Bacteria. Am. J. Epidemiol. 40, (1944).
24. Wells, W. F. Airborne Contagion and Air Hygiene: An Ecological Study of Droplet Infections. (The Commonwealth Fund by Harvard University Press, Cambridge, Massachusetts, 1955).
25. American Society of Heating, Refrigerating and Air-Conditioning Engineers. ANSI/ASHRAE Standard 55-2023 Thermal Environmental Conditions for Human Occupancy. (2023).
26. Centers for Disease Control and Prevention, National Institute for Occupational Safety and Health, Beaucham, C. & Tomasi, S. Evaluation of Volatile Organic Compound Exposures at a Tire Manufacturing Facility. HHE Report No. 2023-0062-3404. (2024).
