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With cold and flu season on the way, patients may be tempted to spend a little money in an effort to avoid getting sick. Specifically, you may field a few questions about buying and using indoor air cleaning devices to prevent the spread of respiratory infections in their homes or offices. 

Trouble is, it can be hard to make recommendations because many air-cleaning technologies look or sound promising. But according to a recent scoping review of indoor air cleaning technologies published in the Annals of Internal Medicine, a lot of gaps in the knowledge still exist. That can make it challenging to steer patients in the right direction. 

About Those Gaps

Titled “Engineering Infection Controls to Reduce Indoor Transmission of Respiratory Infections: A Scoping Review,” the study explored nearly 700 studies representing almost a century’s worth of research on wide array of engineering infection controls designed to reduce the risk of respiratory infection transmission though indoor air.

The researchers noted that some controls have shown that they can reduce indoor transmission of respiratory infections in people, such as germicidal ultraviolet energy, ventilation, and portable air filtration. However, a number of gaps exist in the literature about the efficacy and outcomes of many engineering infection controls, as well as their safety. 

For example, researchers found that only 9% of the studies they reviewed examined whether the technologies actually reduce illness in people. Most studies relied on surrogate outcomes. 

“Overall, few studies directly examined the effectiveness of engineering control interventions on human-to-human indoor transmission of respiratory pathogens,” they wrote. 

Although the lack of research can be attributed to a number of factors, including ethical requirements for human participation in research, the researchers suggested that future researchers test air-cleaning technologies for effectiveness in real world settings, such as classrooms and healthcare facilities, and track the numbers of actual infections. 

The researchers were also concerned about the lack of information about the potential harm that could be caused by some technologies. Only a handful of studies exploring pathogen inactivation technologies also explored potentially harmful byproducts such as ozone, carbon monoxide, formaldehyde, hydroxyls, or hydrogen peroxide. 

More information about the potential risks associated with some products or systems before making a purchase could be helpful, said study co-author Lisa Bero, PhD, professor of internal medicine in the Center for Bioethics and Humanities at the University of Colorado Anschutz Medical Campus, Aurora. Without that information, many people might just assume the devices are benign, something that runs in the background to remove pathogens and ostensibly make the air better.

“The average person wouldn’t think they would be giving off harmful chemicals at the same time, because a lot of us don’t know how these things work,” said Bero.

What To Do in the Meantime

With these gaps, healthcare professionals may wonder how they can guide patients.

Amiran Baduashvili, MD, associate professor and associate vice chair of education in the Department of Medicine at the Anschutz Medical Campus, one of the study’s co-authors, suggested advising patients to be skeptical when looking at the promises made by the marketing departments of the various technologies and devices. 

“Especially when it comes to infection prevention,” said Baduashvili.

For example, the Environmental Protection Agency (EPA) notes that there is no difference between the smog outdoors and ozone, a lung irritant, produced by ion generators and other electronic air cleaners “despite some marketers’ claims.”

According to pulmonologist William Checkley, MD, PhD, a professor of medicine at the Johns Hopkins University School of Medicine in Baltimore, clinicians can also be mindful of their patients’ underlying medical conditions, as well as their environment, when discussing the issue.

For example, patients with chronic medical conditions such as asthma or chronic obstructive pulmonary disease might especially want to consider using HEPA filters in their home HVAC system to reduce dust, pollen, mold, and other particles in the air. This could also be helpful for people who live in areas with poor air quality. 

They should also be vigilant about changing the filters regularly, said Checkley. 

According to the EPA, a high-efficiency air filters with a Minimum Efficiency Reporting Value (MERV) of 13 or higher can trap smaller particles, such as viruses, so upgrading to a MERV 13 filter could remove more viruses from circulated air. 

However, the EPA cautions that many home systems are equipped with a MERV 8 filter, so it’s important to consult an HVAC professional to make sure the system is prepared to accommodate it. 

Patients don’t have to rely on technology to benefit from better ventilation, though, said Shira Doron, MD, an infectious diseases physician at Tufts Medical Center in Boston. 

“The biggest bang for your buck literally is opening the windows and having air flow if you can, based on the weather,” she said. 

Keep Washing Your Hands

Even if research reveals more information and fills in the gaps about various air-cleaning technologies available for purchase, it would not eliminate the need for infection prevention measures such as hand hygiene and vaccination. Noting that not everyone has the means to purchase devices and technology, Amy Duckro, DO, called such precautions “primary and essential.”

“No one system is ever going to replace the need to wash our hands,” said Duckro, an infectious diseases physician with Kaiser Permanente in Colorado. “No system is ever going to replace the benefit of not being right in front of someone who is sick or not shaking hands with someone who is sick.”

Baduashvili agreed. “Those things are still just as important even if you have the latest and greatest device that promises to clean the air,” he said. 

Primary care providers can also stress to their patients the importance of overall good health when it comes to fighting infections. This can include eating a healthy diet, getting enough good quality sleep, reducing stress, and optimizing underlying medical conditions, said Doron, who is also the chief infection control officer for the Tufts Medicine Health System and a professor at Tufts University School of Medicine.

“To a large degree, respiratory infections are inevitable, so you want to be healthy when you get one,” said Doron.