Comparison of an Antimicrobial Air Treatment Technology with Enhanced Ventilation and Filtration Strategies

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By Gurumurthy Ramachandran, Mitchel W. Simpler, Christopher J. Holliday, and William l. Jordan | November 14, 2022 << Back to Articles Comparison of an Antimicrobial Air Treatment Technology with Enhanced Ventilation and Filtration Strategies

Grignard Pure® is an antimicrobial air treatment product that is released into the air as a vapor, where it contacts and inactivates (“kills”) airborne pathogens. The U.S. Environmental Protection Agency (EPA) has reviewed Grignard Pure for safety and efficacy and approved its use on an emergency basis to reduce airborne levels of the virus that causes COVID-19. Additional information about the health and safety of Grignard Pure is available here: Risk Assessment for Use of Grignard Pure and Inhalation Exposure to TEG in Grignard Pure Products.

This article is the second in a series from Grignard. Access part one here and read part three here.

How does this technology stack up against enhanced ventilation and filtration measures? Grignard Pure is not intended to replace the enhanced ventilation and filtration strategies recommended by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) and the U.S. Centers for Disease Control and Prevention (CDC). Grignard Pure has been deployed as an additional layer of protection for public health in the fight against the COVID-19 pandemic. The product’s label directs users to follow public health officials’ advice, including enhanced ventilation and filtration guidance.

Grignard Pure can be introduced into an indoor space either through application equipment installed in an HVAC system or by a free-standing dispersion unit. Engineering studies show that the aerosol quickly and evenly disperses throughout an indoor space and does so in both small and large spaces. (New Amsterdam Theatre Grignard Pure Proof of Concept Part 1: Enhanced Ventilation Studies and JBB: Grignard Pure Deployment Case Study.) Sensors can measure the level of aerosol in the space. In order to ensure a consistent, safe, and efficacious concentration of Grignard Pure in the air, proprietary software can use sensor measurements to automatically direct the dispersion equipment to maintain Grignard Pure at the concentration level within the EPA-approved concentration range once the target level is reached.

Three criteria are critical to examine when comparing an antimicrobial air treatment with enhanced ventilation and filtration measures. First, the amount of reduction: What percentage of the circulating virus is eliminated? Second, the speed with which the measure works: How quickly does the measure remove virus particles? Third, the mechanism of action—removal versus inactivation of the virus particles: How does the measure achieve its effect?

Percentage reduction

Grignard Pure reduces the level of airborne virus particles by over 99.5% in 10 minutes. This compares favorably with enhanced ventilation and filtration strategies, which can vary considerably depending on the specific measures implemented.

Ventilation—the introduction of virus-free, outside, “fresh” air—depends on the HVAC system’s settings but is rarely more than 15% fresh air per air change.

Ventilation, increasing the number of fresh air changes per hour, removes some of the virus. It also helps by mixing with and diluting the indoor air, thereby reducing uneven concentrations of the virus. The elimination or reduction of “hotspots” may lessen the chance of transmission. Increasing ventilation as the only measure is not enough to protect people from COVID-19.

Filtration is more effective than ventilation, depending on the technology used to filter virus particles from the air. Filtration depends on indoor air circulation through an HVAC system in which either a physical filter or an antimicrobial device has been installed. Physical filters trap a percentage of pathogen particles passing through the HVAC system, but filter efficiency varies. Smaller particles are harder to trap. Also, different types of filters trap more particles based on their size. Further, as ventilation and filtration rely on the flow of air to reach the filter, there is a gap in the protection for those in the immediate vicinity of an infected individual before the air reaches the filter.


Grignard Pure achieves its 99.5% kill rate quickly. By comparison, the speed with which enhanced ventilation and filtration measures work will likely take considerably longer. Both filtration and ventilation depend on the rate of circulation of indoor air, expressed as air changes per hour (ACH), and in most buildings and other commercial indoor spaces, HVACs operate at 0.35–8 ACH (typical ACH is 2–4).

Percentage kill and speed, taken together, tell a compelling story. While Grignard Pure lowers the level of airborne virus particles by 99.5% in less than 10 minutes, The CDC estimates that it would take about 90-180 minutes for an air filtration system to remove an equivalent amount of virus without an active shedder in the space.

Mode of action

Grignard Pure inactivates virus particles in the air of an indoor space. By contrast, ventilation and filtration remove particles without necessarily inactivating them. Replacing virus-laden air with fresh air lowers the level of virus particles, but filtration using physical means simply traps the virus in the filtration medium, potentially making it hazardous. Finally, filtration and ventilation effectively remove viruses and bacteria from the space but may do little for respiratory droplets that carry these pathogens.

While Grignard Pure is a scalable approach to protection in indoor spaces of any size, engineering considerations limit the extent to which ventilation and filtration measures can be employed. Challenges include:

  • The need for engineering assessments prior to making any enhancements to ventilation and/or filtration.
  • Limitations in a building’s infrastructure create more difficulty in making meaningful upgrades to the ventilation rates.
  • Increasing the amount of outside, fresh air increases operating costs to condition the air prior to circulating inside.
  • Increasing filtration efficiency can reduce the airflow rate through the equipment. Many new guidelines for large spaces like malls and older venues cannot be achieved with existing installed equipment because it lacks sufficient power to maintain an adequate ACH level.
  • Increasing ventilation or filtration efficiency also requires more energy, increasing the release of harmful greenhouse gases.
  • Removing filters when virus particles are present can be hazardous and specific procedures are required.

In conclusion, Grignard Pure is not intended to replace the use of enhanced ventilation and filtration measures. It is, however, a low-risk, effective, practical, and quicker way to reduce airborne concentrations of virus particles. Grignard Pure should be used as an added layer of protection in conjunction with other measures recommended by public health officials. Using Grignard Pure, together with the suite of other public health actions, could dramatically reduce the level of circulating virus in locations where large groups of people gather and where the risk of continued transmission is still high.

Read the full white paper here.

Note: Grignard Pure is only available in those states under an EPA emergency exemption. Grignard Pure is in the process of seeking EPA authorization for general, nationwide use.

About the Author.

Gurumurthy “Ram” Ramachandran, Ph.D. 
Professor, Department of Environmental Health, and Engineering |
Bloomberg School of Public Health, The Johns Hopkins University 

Dr. Ramachandran joined Johns Hopkins University in 2016. He is the director of the Johns Hopkins Education and Research Center for Occupational Safety and Health funded by the National Institute for Occupational Safety and Health (NIOSH). Starting in July 2019, he was also appointed as deputy chair for the Department of Environmental Health and Engineering. 
He has conducted research in various areas relating to human exposure assessment in occupational, residential, and outdoor settings. His research has included the development of occupational exposure assessment strategies for airborne contaminants.

He has conducted pioneering studies in occupational hygiene decision-making that synthesizes mathematical exposure models, monitoring data, and probabilistic expert judgment within a Bayesian framework. He has led or participated in multi-disciplinary teams engaged in numerous community and occupational exposure assessment and epidemiological studies in the US, India, Canada, and Bangladesh.

He collaborates with colleagues in International Health on epidemiological studies in Bangladesh relating to cookstove emissions, with toxicology colleagues on designing exposure chambers for animal studies, and colleagues in the SOM on lung dosimetry modeling. He is co-leading the Exposome Collaborative at Johns Hopkins University. 
He has served as a member of the Board of Scientific Counselors to the National Institute of Occupational Safety and Health (NIOSH) and advisory committees for the National Academy of Sciences (NAS) and the U.S. Environmental Protection Agency (USEPA). He is also serving on the editorial boards of the Annals of Work Exposures and Health and the Journal of Occupational and Environmental Hygiene. He has a bachelor’s degree in Electrical Engineering from the Indian Institute of Technology Bombay, a master’s degree in Environmental Engineering, and a Ph.D. in Environmental Sciences and Engineering from the University of North Carolina. 

Mitchel W. Simpler, PE, FACEC | Partner
Managing Partner Emeritus

Mitch Simpler joined JB&B, a global consulting engineering firm, in 1977 and currently serves as partner after having served as Managing Partner from 2012-2018. He has acted as project manager and partner-in-charge on life/health science institutions, health care facilities, high-rise office buildings, museums, residential and mixed-use buildings, as well as hotels.

Simpler’s list of notable projects in the life science sector spans the past 40 years, including premier laboratory facilities and research centers in New York City, such as the Jerome L. Greene Science Center at the Columbia University Manhattanville campus, New York Genome Center, Mount Sinai’s Hess Center for Science and Medicine, Weill Cornell Medical College’s Belfer Research Building, MSK’s David H. Koch Center for Cancer Care and Rockefeller Research Laboratories, Cornell University’s Biotechnology Building, and NYU Langone Health’s Smilow Research Building and Skirball Institute of Biomolecular Medicine. 

His experience extends around the world to China, with the Innovation Center at Duke Kunshan University in Kunshan and the Rohm & Haas Research Center in Shanghai.

Simpler is a fellow of the American Council of Engineering Companies (ACEC) and recently served as the National Chairman of ACEC. He is also a founding member of NYC Builds Bio+.

Ed Bosco, PE, LLED AP BD+C 
Managing Principal 
ME Engineers 

Growing up, Bosco was inspired by visits to EPCOT and the National Air and Space Museum. Now he heads the New York office of the firm that engineered them. He enjoys working on some of the world’s most interesting and challenging projects and the opportunities these projects create to mentor and inspire young engineers. 

Bosco brings fresh thinking to the design challenges of complex critical systems and spaces. With 30 years of experience in new construction and renovation, central chiller plants, critical electrical systems, fire protection, and critical care space upgrades, Bosco’s approach delivers designs that creatively solve problems and balance performance, value, and cost. 

He teams with architects, owners, and constructors to develop the phased thought necessary to renovate mission-critical, critical care spaces, and high-profile public assembly spaces where downtime is not an option. Some of the most significant examples of this include the US$1 billion phased transformation of Madison Square Garden, a 10-year phased infrastructure replacement project at Westchester Medical Center, reinforcement of the Nasdaq MarketSite facility at Times Square, and the $600 million renovation of the NYC campus that hosts the U.S. Open Tennis Tournament. 

Christopher J. Holliday, P.E.
Senior Vice President National Vehicle Engineering

Holliday is a senior vice president and leads the National Vehicle Engineering practice for STV Incorporated. Holliday serves as the office manager for STV’s Philadelphia office, home to 105 engineering professionals.

With over 35 years of engineering experience, Holliday is a licensed mechanical engineer in Pennsylvania, a member of the American Passenger Transportation Association (APTA), the American Society of Mechanical Engineers (ASME), Women’s Transportation Seminar (WTS), the National Society of Professional Engineers (NSPE) and the Pennsylvania Society of Professional Engineers (PSPE).

Holliday has assembled a team of experts specifically to address the challenges that public transportation agencies face in both recovering from the impact of the pandemic and in making the full transition to zero-emission vehicle fleets.

Working with these agencies to regain the trust of the riding public and become more resilient against a future pandemic has driven the exploration of novel solutions around a number of emergent technologies. Holliday’s early career working as an application engineer for an investor-owned electric utility gained him key insight into the economics of electricity purchases, rate structures, and utility operations, as well as the role of Hydrogen as a renewable energy currency.

William L. Jordan 
Former, EPA Office of Pesticide Programs 

William L. Jordan currently works as an independent consultant to non-governmental organizations, law firms, and companies on pesticide and food safety issues. He provides advice based on his knowledge and experience drawn from over 40 years of service in EPA’s Office of Pesticide Programs (OPP) and Office of General Counsel. He has also served as an expert witness in federal District courts and in arbitration proceedings.

Prior to ending his federal career, Jordan served in a variety of positions in OPP, most recently as the Deputy Director for Programs. He has handled a wide variety of cross-cutting science and policy issues in areas such as food safety, human research ethics, pesticide labeling, endangered species protection, biotechnology, and nanotechnology.

Jordan played a significant role in the development of the legislation that became the Food Quality Protection Act of 1996. He was responsible for coordinating the development of documents describing the major science policies that EPA applies in implementing this law. In addition, he has been involved in diverse policy and regulatory actions affecting pesticides, ranging from implementation of the worker protection standards to trade policy to data requirements regulations.

He has also been a guest lecturer at Cornell University and a staff member of the President’s Council for a National Agenda for the Eighties. He has a law degree from Georgetown University and an undergraduate degree from Princeton University.