How safe is karate right now?

Before getting too far into this article I’d like to make sure the readers know a few things.  I am not a doctor nor am I an epidemiologist.  I have no background in medicine or medical research.  Please do not use this article as the basis for any decisions regarding your health or the health of people around you, including opening/closing of any businesses.  This article is strictly for informational purposes.  There are no political references either and I would appreciate that any feedback or comments please refrain from expressing any political views.  The following information are simply my observations and analysis.  So, without further ado, let’s get into it.

Several times a week, I walk from my home to my karate studio.  I walk the 1.5-mile trek along the main street in my neighborhood which takes me through the business district.  Since March I have also kept very in tune to the closings and re-opening restrictions placed on businesses, being a small business owner myself.  I would often wonder where some of the restrictions and guidelines came from as they did not make sense.  As I took my walk to work, I would see firsthand how several types of businesses implemented these restrictions and guidelines in their reopening efforts.  The analytical brain in my head started to spew out questions that I needed answers to.  I even tried calling several of my local, county, and state officials but never got a hold of any concrete answers.  Perhaps with more effort I could have eventually reached someone with the answers I seek but I simply don’t have time to be on hold for several hours.  So, my brain was left unchecked and the following is what it came up with.  Please note that this is a theoretical, quick and dirty, analysis.  I have cited sources when appropriate, but this is certainly not a research paper quality work.

The following analysis is a comparison of 4 types of businesses.  I have witnessed first-hand these businesses operations and implementation of the state restrictions.  I am not going to name specifically any of the businesses.  All of these businesses are operating in accordance with the state restrictions, at least from what I have observed.  I am not being a snitch or whistleblower as these businesses are seemingly doing the right thing.  I am using these 4 businesses since they are all different and have different restrictions.  I intend to show that the restrictions have not been set forth correctly.

Before going any further, the following assumptions are being made for all four businesses:

  1. They all have equally effective ventilation systems
  2. Occupants adhere to social distancing 100% of the time
  3. Surfaces are cleaned in the same, thorough manner 
  4. Masks are worn by all occupants
  5. 100% of exhaled particles are airborne and stay airborne for 3 hours (more on this in a minute)
  6. Each business has the maximum, currently restricted, occupancy for one hour 
  7. All occupants are healthy adults who have the following stats
    • 20 breaths per minute
    • Each breath has a volume of 4L
    • Each breath contains 50 particles per L

For my analysis, I am going to determine how many airborne particles occupants are exposed to in order to determine level of safety.  I am conservatively assuming that all exhaled particles are airborne or aerosol and remain in the air for up to 3 hours (versus droplets that can travel up to six feet and give us or social distancing guidance).  It is unknown at this time if COVID19 is airborne, only in droplets, or some combination of the two.  If we assume 100% perfect social distancing, thorough cleaning of surfaces, hand washing, and everyone refraining from touching their faces, we can neglect the droplets for now.  Again, this is theoretical and should not be used as the basis of any safety decisions.

The four businesses I will be analyzing are: a large chain supermarket, a midsize fitness studio, a small hair salon, and my own martial arts studio.  For each business, the following analysis was done:

Building volume = (building sq ft) x (ceiling height)

Number of breaths per minute = (max occupancy) x 20 breaths/min

Number of breaths in one hour = (# breaths per minute) x (60 min/hr)

Total volume of exhalation in one hour = (# breaths in one hour) x (4 L/breath)

Total particles exhaled in one hour = (total exhaled volume) x (50 particles/L)

Number of particles/cubic foot = (total exhaled particles) / (building volume)

I argue that the total number of particles per cubic foot is an indication of how safe something is.  A few more variables before the results:

Supermarket ceiling height = 20 ft

Supermarket square footage = 20,000 sq ft

Supermarket max occupancy = 165 (1 person per 120 sq ft)

Fitness ceiling height = 12 ft

Fitness square footage = 1,500 sq ft

Fitness max occupancy = 14 (they have a sign on the door stating this number)

Salon ceiling height = 10 ft

Salon sq footage = 1,000 sq ft

Salon max occupancy = 8 (limited to 50% capacity)

Karate ceiling height = 12 ft

Karate sq footage = 2,500 sq ft

Karate max occupancy = 10 (5 per class, 1 instructor, assume 4 spectators)

The ceiling heights and square footages are mostly approximations based on observation.  When applicable, I looked up actual building square footage.  Max occupancy numbers are based on either stated explicitly by the business or are the max occupancy stated by state guidelines.  The karate school numbers are accurate as it is my business.

Using all of the above information yields the following results:

Supermarket = 132 p/cu ft

Fitness studio = 186 p/cu ft

Hair salon = 192 p/cu ft

Karate school = 80 p/cu ft

The above data is the number of exhaled particles in the air per cubic foot of space.  You can think of this as how many particles each person in the building is exposed to.  

Before I give my final analysis of the data, there are a few things to consider.  First, the supermarket data is most likely lower since rarely are supermarkets at max capacity.  The fitness studio and martial arts studios are likely higher since exercise will cause more exhalation on average.  The hair salon is also likely higher since it is impossible to social distance while getting your hair done.  Lastly, state law allows for participants doing “strenuous exercise” to not have to wear a mask, even when indoors.  I have witnessed the fitness studio participants not wearing masks on several occasions.  Their number is likely much, much higher (masks can reduce the number of airborne particles by an average of 55%).

Based on this analysis, I have made the following conclusions.  The restrictions set forth are arbitrary and do not take into account enough variables.  I am not determining which of the 4 businesses are the safest (sorry if the title of the article got you hooked).  That is for you to decide, I have simply supplied some data and information to help you decide.  As long as all businesses follow social distancing, wear masks, and follow cleanliness standards, their operations should be limited based on an analysis that looks something like this, not an arbitrary throw of a dart or a spin on the random restriction roulette wheel.

Another reason why the restrictions as set forth do not work is, they are based solely on business type. Building size, ventilation, HVAC systems, and overall cleanliness standards vary greatly in every industry. An 8,000 sq ft karate studio that teaches kids has the same restrictions as an 800 sq ft yoga studio that teaches only adults.

Furthermore, every state in the country has different restrictions.  Do people breath differently in Idaho than they do in Washington?  It is frustrating that things as important as people’s lives and livelihoods are not being considered equally across the country.

I would like to reiterate that I am not campaigning for businesses to open or for them to close.  That is above my pay grade.  I do feel though, that these decisions are being made based on either no data (arbitrary) or incorrect data (not taking into account all variables).

If you are trying to control the spread of any airborne illness, it only makes sense to me to place restrictions on all businesses equally based on what is deemed to be a safe level of exposure to airborne particles.

But, as Bill Maher would say, that’s just my opinion, I could be wrong.

Other Limitations

Some other random thoughts and limitations that could be used to refine the analysis.

  1. Determine social distancing effect.  Factor in time spent within another person’s 6 foot sphere of influence.
  2. Determine effect of overall time spent open.  For instance, my martial arts studio is open about 6 hours, 5 days a week.  The supermarket is open 24 hrs a day, 7 days a week.
  3. Determine effect of heavier breathing when exercising, talking, etc.
  4. Determine the effect of age.  Kids take different breaths than adults.
  5. Determine the effect of touching things (items in a grocery store, pads at a karate school, equipment at a fitness studio, door handles, salon chairs, etc.)
  6. Percentage of droplets vs airborne particles and how likely the virus would be in either


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