Charles Call, Ph.D.

Public trust in the built environment has evaporated. We can recover. 

Creating public trust that indoor spaces are safe for workers- and the public- will be challenging. Success in the New Year depends on a successful rollout and high uptake of the vaccines that are being launched. But between now and when we achieve a high level of herd immunity, we can be proactive. Environmental sampling combined with near-real-time analysis can increase the safety and reduce anxiety associated with indoor air. Let’s explore how.

It is now widely recognized that respiratory aerosols can remain airborne for long periods of time. Viruses can remain viable for long periods of time and are ubiquitous in the built environment, but research into their impact on health was lagging, at least until now. 

The Moraska team at Queensland University of Technology demonstrated that pseudomonas bacteria can remain airborne and viable (infectious) for 45 minutes or more. Prof. Lednicky and co-workers have recently shown by direct measurement that people with COVID-19 exhale breath aerosol that contains viable virus particles. More worrying yet, it was recently shown that COVID-19 patients can exhale millions of viral particles per hour, usually during the earlier stages of the infection. This is consistent with anecdotal descriptions of super spreader events driven by pre-symptomatic individuals. In light of the newer even more contagious strain that has emerged and is rapidly spreading across the globe, these are indeed frightening observations.

People can become symptomatic, or even dangerously ill, very quickly. One person was suffering from relatively modest symptoms when he boarded a plane, but died in flight. It stands to reason that people can become spreaders very quickly as well. One moment they are not infectious to others, but perhaps an hour to later, they might become very infectious to others. 

Bioaerosol sampling and analysis techniques have been developed and validated for research, proving that SARS-CoV-2 is spread as viable exhaled breath aerosol. Is it possible to develop cost-effective procedures to operationalize on-site rapid sampling and analysis of airborne SARS-CoV-2 virus concentration in order to minimize the risk that employees or the public will be exposed to an infectious dose?

Rapid environmental sampling and near-real-time detection has the potential, if operationalized, to identify a hazardous environment quickly. This can be done by sampling on factory floors and office buildings to limit the dose received by those that work near the spreader. By limiting contact time with spreaders, employers will have increased ability to keep their workforce healthy. Sampling and near-real-time analysis will be most effective when the sampling and analysis is done frequently due to the episodic nature of virus shedding. Similarly, the effectiveness of the method is highest when the total time required for sampling and analysis is short, preferably less than an hour, or better yet, less than 15 minutes. These two factors, frequency and rapidity of testing, impact the dose received by other employees working in proximity to a spreader.

Tyson Foods reported that they spent $300M in 2020 on “thank you bonuses” to induce employees to show up for work. When employees see that employers are proactively seeking to identify co-worker that are spreaders, they will naturally feel better about coming to work. 

Real-time sampling and analysis should be implemented to help reduce employee exposure to SARS-CoV-2 and thereby improve public confidence in the health and safety of the built environment.


The views expressed in this blog are those of the author.


J.A. Lednicky, M. Lauzardo, Z.H. Fan et al.  Viable SARS-CoV-2 in the air of a hospital room with COVID-19 patients.  International Journal of Infectious Diseases 100 (2020) 476–482

Jianxin Ma, Xiao Qi, Haoxuan Chen, Xinyue Li, Zheng Zhang, Haibin Wang, Lingli Sun, Lu Zhang, Jiazhen Guo, Lidia Morawska, Sergey A. Grinshpun, Pratim Biswas, Richard C. Flagan, Maosheng Yao  Exhaled breath is a significant source of SARS-CoV-2 emission.  doi:

Johnson, G.R., et al. A novel method and its application to measuring pathogen decay in bioaerosols from patients with respiratory disease.  PLOS ONE (2016).  doi:

Prussin, A.J., Belser, J.A., Bischoff, W. et al. Viruses in the Built Environment (VIBE) meeting report. Microbiome 8, 1 (2020).  doi:

Public Health Guidance for Community-Related Exposure.  Center for Disease Control and Prevention