By Jim Rosenthal, CAFS
As of today, August 8th, US health officials have reported nearly 5,000,000 cases of Covid-19 (officially SARS-Cov-2). Deaths are over 161,000. This is not just the flu.
One of the reasons the disease has spread so fast and so widely is within-household transmission. It is estimated that one in five people living in the same household with someone who has Covid-19 will contract the disease. We tell people who have Covid-19 to self-quarantine. But by doing so we often put other family members at risk.
And what directions do we give to Covid-19 sufferers who go into self-quarantine? Wash your hands. Avoid contact with any other household members. Clean surfaces. Wear masks. Try to stay at least 6 feet away from others. Ventilate with fresh air whenever possible. We know the drill, but we are missing a very effective added element – differential pressure.
We have all heard about, read about and seen on TV what hospitals use for Covid-19 patients – isolation rooms. These make sure that all of the contagious virus particles coming from the sick individuals remain in the room. The reason why they stay in the room is a physical force called negative pressure. Creating negative pressure is pretty simple. You push more air out of the room than you take in. In the case of an isolation room a fan is used to force air out. That air goes through a HEPA filter (for more information on HEPA filters see: https://www.texairfilters.com/understanding-how-hepa-air-filters-remove-covid-19-from-the-air/) and then out into the outside environment. A properly designed and maintained isolation room is very effective at containing dangerous particles.
So how does this apply to the Covid-19 patient confined to their home? Simple. You make part of the home into a negatively pressurized isolation room. Seal off a room (preferably with a bathroom) in the house. Then use some kind of a device to push air out of the room. If you happen to have a fan with a HEPA filter attached (called a negative air machine), that would be great. That is the best option. However, if you don’t have an $800 to $1,000 negative air machine at your disposal, you can use a “Box Fan with a MERV 13 Filter.” The device should be placed in a window or door going to the outside. It needs to be pointed out.
We have just done some testing on the “Box Fan with a MERV 13 Filter” air cleaning device and found that it was very effective at removing particles in the 1 to 10 micron range. Many experts believe that viable airborne Covid-19 particles are in this range. This article explains how to make a “Box Fan with a MERV 13 Filter.” It is not difficult. It is not expensive. But it works.
How well does the negative pressure work in a house to control particles? I have experience with that. My home was built in 1965. We have been remodeling virtually every room – one room at a time for the last 5 to 6 years. I know about negative pressure. So I tell every contractor that they must put up plastic sheeting sealing off their work area. Then I tell them to place a fan in a window somewhere in this area – blowing out. The result? All of the construction dust from cutting sheetrock, sanding surfaces, sawing wood, etc. is confined in the work space. None of this dust goes into the rest of the house.
The same would happen with airborne Covid-19 particles. Seal the area and then push air to the outside. Negatively pressurize the space. The particles will either stay in the enclosed space or be pulled into the filter. Most importantly, they will not invade the rest of the house and expose the other residents to Covid-19.
But there is another consideration – ventilation. Nature loves to have equilibrium. For every force, there is a counter force. So when you put that fan in the window to create the negative pressure in the room of the Covid-19 patient, the air in the balance of the indoor environment will seek to enter that room. It comes under and around the door, through windows, between cracks, and around or through anything used to create the “seal.” The ventilation air is needed and will not stop the effectiveness of the “isolation room” as long as the negative pressure in the room exceeds the pressure outside of the room.
One needs to measure the balance between the two spaces. That is pretty easy to do with a strip of tissue. Hold it up by an opening (around the door for example) going into the negatively pressurized room. The paper should go towards the “isolation room.” Any particles containing Covid-19 will either stay in the room or be pulled outside by the fan in the window.
It helps to open a window or windows to supply ventilation air. That ventilation air will help to dilute any other airborne potentially contagious particles, reduce CO2 levels and provide for a safer indoor environment.
This same concept of containing Covid-19 should be applied in other areas. Nursing homes, college dorms, apartments, office buildings, and any other space where it is possible to seal, remove viral particles and create negative pressure should adopt this procedure as soon as possible. It is a proven, effective way to limit exposure to Covid-19 – even for people who live or work in an indoor environment where someone has the disease and is contagious.