Low-cost point of emission air purifiers can reduce airborne transmission of pathogens, says study

In a study conducted at the Monash University, Australia, scientists have examined the efficacy of portable air purifiers combined with a hood in reducing virus aerosol transmission and protecting healthcare workers from workplace contamination. The study is currently available on the medRxiv* preprint server.


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative pathogen of coronavirus disease 2019 (COVID-19), is an enveloped RNA virus of the human beta-coronavirus family that primarily transmits via large respiratory droplets.

However, some recent studies have highlighted the possibility of airborne transmission of SARS-CoV-2 via small respiratory aerosols that remain suspended in the air for prolonged periods of time and can travel long distances.

Air exchange/filtration system applied at the point of emission can effectively reduce the spread of pathogen-containing aerosols in a non-ventilated room. In this strategy, a hospital-grade air purifier with a high-efficiency particulate air (HEPA) filter is used together with a containment tool such as a hood. However, this method is very expensive and requires changes in existing infrastructure.

The study

In the current study, the scientists have introduced live bacteriophage virus-containing aerosols into a non-ventilated clinical room and assessed the efficacy of a low-cost, commercial-grade air purifier and hood in reducing environmental and skin contamination.

Moreover, they have assessed whether this point of emission aerosol controlling strategy can increase the level of protection provided by routinely used personal protective equipment (PPE) among healthcare workers.

Specifically, they have tested surface contamination of the clinical room and skin contamination of a healthcare worker who was wearing a gown, gloves, face shield, and a non-fit-tested N95 face mask. The healthcare worker remained inside the aerosolized room for 70 minutes. To measure skin contamination, swab samples were collected from the forearms and back of the hands, neck, forehead, and skin areas covered by the N95 mask.   

Important observations

In control conditions where no air filtration or hood was applied, a significantly high surface contamination and a modest level of skin contamination underneath the PPE were observed. The skin contamination was highest on skin areas beneath the N95 mask. In contrast, significantly low surface contamination and almost no skin contamination were achieved by implementing a commercial-grade air purifier and hood. As expected, a hospital-grade air purifier completely prevented both surface and skin contaminations.

Taken together, these observations indicate that in a poorly ventilated clinical room with a high number of virus-containing aerosols, routinely used PPE provides only partial protection against skin contamination to healthcare workers who are exposed to aerosols for a prolonged period of time.

A comparatively higher skin contamination noticed beneath the face mask could be due to the suction generated by respiration. A high level of protection against skin contamination offered by both commercial-grade and hospital-grade air purifiers indicates that even a low-cost air filtration method is sufficient to enhance the effectiveness of PPE.   

Study significance

The study highlights the importance of a simple, low-cost point of emission air filtration strategy in preventing airborne transmission of SARS-CoV-2 in high-risk setups like hospitals. According to available literature, the mortality rate is considerably high among in-hospital patients and healthcare workers who acquire SARS-CoV-2 infection while receiving and providing treatment, respectively. The air purification strategy described in the study can significantly reduce the level of exposure in these high-risk groups.

*Important notice

medRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
Dr. Sanchari Sinha Dutta

Written by

Dr. Sanchari Sinha Dutta

Dr. Sanchari Sinha Dutta is a science communicator who believes in spreading the power of science in every corner of the world. She has a Bachelor of Science (B.Sc.) degree and a Master's of Science (M.Sc.) in biology and human physiology. Following her Master's degree, Sanchari went on to study a Ph.D. in human physiology. She has authored more than 10 original research articles, all of which have been published in world renowned international journals.


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