Brandon Lawrence, MD 11/9/20 11:54 AM 6 min read

What is Negative Pressure?

When hospital patients either have or are suspected to have an infectious illness, like tuberculosis or COVID-19, or they are especially susceptible to contracting an infection from other people, they often must stay in an isolation room. These rooms are designed using negative pressure to prevent airborne diseases from leaving the room or with positive pressure to prevent infectious diseases from entering the room.

As the number of COVID-19 cases continues to rise rapidly in the United States, many hospitals are relying on negative pressure rooms to keep patients under investigation (PUIs) from spreading the coronavirus to other patients, hospital visitors, and healthcare staff.

While many people have heard of these negative pressure rooms, many are not exactly sure of how these rooms work.


The term negative pressure is somewhat of a misnomer. In an absolute (perfect) vacuum, pressures approach zero atmospheres (atm). Considering this fact, the idea of a negative pressure device or room might seem a bit confusing. A better way to think of it, rather than “negative” or “positive,” is the difference between this pressure and the ambient pressure that surrounds it. The regular atmospheric pressure on earth is 1 atm or 760 Torr (unit of pressure). So, in a negative pressure room, the pressure within the chamber is lower than the regular atmospheric pressure outside of the room.

These negative pressure rooms and devices are used effectively in healthcare to reduce the spread of infectious illnesses.

Most infectious diseases are transmitted through aerosols and droplets. Droplet transmission occurs when a symptomatic patient coughs, sneezes, or otherwise spreads infectious droplets through the air.

While some of these contagions form large droplet nuclei and fall out of the air without spreading particularly far from the patient, others are aerosolized, allowing them to remain suspended in the air. This allows for airborne transmission, which is especially harmful when it comes to spreading COVID-19. 

When an infected person coughs, sneezes, or speaks during a procedure that causes aerosolization, like intubation or nebulizer treatments, they produce high concentrations of infectious aerosols. Because these particles are airborne and highly concentrated, they put healthcare workers and other people who are around these patients at risk.

This is where different tools, like negative pressure rooms, make a difference.

Negative pressure rooms actively remove contaminated room air via vacuum filtration with HEPA filters, and they pump non-contaminated air back into the room. This vacuum technology creates a negative pressure gradient from within the room to outside, preventing the internal air from leaving the space between the room and reducing the spread of infectious diseases.

Enter the SCONE™ - A Self Contained Negative Pressure Environment.

While negative pressure rooms are a helpful resource, they are not a perfect solution for preventing the spread of COVID-19.

The speed at which the contaminated air is moved toward the outward ventilation depends on the number of “air changes per hour.” Negative pressure rooms typically produce 12 air changes per hour, which takes between 35 and 80 minutes to clear the contaminated particles from the room. This aerosol clearance time, or ACT, while unavoidable, creates a logistical bottleneck, significantly decreasing hospital throughput.

Nebulizer treatments and intubations occur very frequently, and these negative pressure rooms must stay sealed until the 100% aerosol clearance time. In hospitals where there are only a small handful of these rooms available, providing patient care using these rooms is a logistical nightmare.

That’s why a negative pressure resource like the SCONE™ is more important now than ever.

The SCONE™ provides barrier protection with active filtration of infectious particles to prevent these particles from leaving a patient’s environment. With the use of the SCONE™ and PPE, the risk of healthcare workers contracting any aerosolized or droplet illnesses is drastically reduced. Even with the portholes open, our testing shows with the SCONE™ that the number of particles expelled was zero.

Thanks to the two suction ports on the SCONE™, the automatic clearance rate is under five minutes, markedly less than that of a negative pressure room. This helps increase hospital throughput while decreasing the need for negative pressure rooms and improving room turnover after aerosol-generating procedures.

The SCONE™ has been authorized by the FDA for Emergency Use. Click the button to connect with us and learn how to bring SCONE™ protection into your healthcare facility.

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Brandon Lawrence, MD

Dr. Lawrence is an Emergency Medicine Physician born and raised in Phoenix, Arizona, currently working in the west valley. From the start of the pandemic, he has been passionate about being on the forefront for care of his patients and protection for his fellow healthcare professionals. In his spare time, he enjoys spending time with his family, exercise and podcasting. He graduated from University of Arizona with a Bachelor's in Biochemistry and Michigan State University for his Medical Degree.
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