Most of those issues seem moot to me. In an enclosed space with recirculating air and a customer who is shedding virus, the air in the part of the restaurant where that customer is sitting will accumulate the highest levels of virus particles you’re likely to encounter outside of a hospital, care home, or public transportation.
Thank you for such a well articulated and thoughtful post.
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The complete post was great and insightful and the last sentence summarizes it correctly - it’s hard not any longer be able to eat out but even when restaurants are open again it won’t be worth the risk for a long time.
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HVAC experts and industry publications have been discussing how recirculating air can spread SARS-CoV-2 since mid-February.
No preview for some reason: Guidance for Building Operations During the COVID-19 Pandemic | ashrae.org
The CDC has guidelines against using recirculated air in ride-sharing vehicles, ambulances, and when transporting infected people, but not yet for buildings, buses, or trains that I can find.
https://www.cdc.gov/coronavirus/2019-ncov/hcp/guidance-for-ems.html
https://www.cdc.gov/coronavirus/2019-ncov/community/organizations/rideshare-drivers-for-hire.html
New poster, long-time lurker… Does anyone know what minimum % of occupancy restaurants need to sustain in order to keep the in-house dining part of the business profitable? In other words, if you are already paying rent, have a cook to service take-out and a person at the register, what other cost is there beyond bringing back waiters / bussers, etc? I’m totally uneducated on the restaurant industry but fascinated by the economics of it… but i’ve seen proposals in Norcal about allowing restaurants to operate at 25% occupancy and I’m curious to understand if it’s even worthwhile for an owner to do so.
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Most restaurants, the margins are so slim that any reduction in peak capacity would make them unprofitable. See the article I linked to here:
I am well acquainted with the dangers of air conditioning. Many years ago I got sick in the middle of the summer and was finally diagnosed with pneumonia. It took a good 3 weeks to get over it. I was working in a test kitchen office and my illness was traced back to an air conditioner that had not been serviced for many years and was loaded with mold. Needless to say the air conditioner was removed and a new one put it before I came back to work.
Your point is well taken, but for me, it’s just one of many issues that are going to have to be resolved. I think the financial viability of any food service operation these days will depend upon multiple factors of varying complexity and importance.
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Here is a partial list of expenses restaurants usually cover, there are more, these are just the ones I can think of off the top of my head:
Rent
Salary & wages…and possibly benefits if offered
Cost of food
Cost of beverages including liquor
Disposables…i.e. to-go packaging
Cost of cleaning/chemical supplies
Utilities
Trash pick-up
Linen or laundry service…even if a resto doesn’t use linen tablecloths or napkins, they still have towels and aprons.
Insurance…including worker’s comp
Repair services for things like coolers, ranges, grills, fryers, steamtables
Hood cleaning service
Replacement of service wear that gets broken or stolen…i.e. dishes, silverware, etc
Sales tax remittance to State of CA
Carbonated beverage tax remittance to State of CA
Business licenses as required by each county
Local, State and Federal business taxes
I’ve seen/read interviews with multiple chefs and the majority of them are saying that 50% occupancy will stretch them financially. Restaurants are notoriously expensive to run and notoriously under capitalized. The minimum wage in CA is $12.00, in San Francisco it’s $15.50+ and $14.25 in Los Angeles. If an employee works over 32 hours/week the employer is required to provide benefits, altho’ there are exceptions to this if there are fewer than a set number (which I’ve forgotten because it’s late) of employees. Payroll expenses have been eating into restaurant profits for at least the last 7-8 years.
The old traditional model used to be for food cost under 30% range and labor (including any benes) in the low to mid 20% range +/-… That model is totally out the window now and has been for a while as payroll costs have escaled.
I was in some aspect of the food business for 40 years, primarily in the non-commercial sector. Let’s just say I’m really glad I retired 2 years ago 
I would not want to be dealing with this mess right now.
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Here’s my (very) simple back of the envelope model.
Draw a simple graph.
X = revenue per cover x covers. This will be a straight line from bottom left to top right.
Y = fixed cost + variable (incremental cost per cover). This will be astronomical at low cover count, at the left. Sloping down steeply as increased covers spread out the fixed costs.
The # of covers where the two lines intersect is the break even.
Extremely simplified model. Plenty of gray area as to what is fixed vs incremental. Some variables (perishables, labor) will need to be “fixed” at basic levels.
If your number of reduced seats x projected turns does not yield break even covers, time for some hard decisions.
@DiningDiva, whattaya 
think?
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A simple and elegant explanation, I like it 
. There is always wiggle room or gray area in decision making. How much may depend upon how savvy the restaurant operator is, their location and how well capitalized they are.
I think that no matter how this pandemic plays out, it will provide operators with a wide open opportunity to do some creative thinking to reimagine, reconfigure and reinvent their restaurants. It’s pretty clear that the same ol’, same ol’ isn’t going to work any more. Time for something new. I also think there are a fair number of restaurant owners out there right now in your “hard decision” category.
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Much of metro Atlanta’s restaurant industry knew immediately that reopening would take time and that there wouldn’t be a rush back in the name of expediency. Hugh Acheson, a well-known Atlanta restaurateur, tweeted on April 21 that “No one tells me when to open.” Using the hashtag #GAHospitality, 50 restaurant owners representing 120 restaurants took out a full-page ad in the Atlanta Journal-Constitution giving their reasons for remaining closed for dine-in service despite being allowed to reopen. As we head into mid-May there have been no major updates on when Atlanta’s dining scene will reopen.
Which confirms this story from a few weeks ago:
Sure, there are lots of issues, but social distancing, seating only a portion of seats, servers washing hands even more than usual and wearing masks, and putting up barriers are just theater if recirculating air is spreading virus particles among customers, who obviously can’t wear masks while eating and drinking. And using disposables? That’s anti-scientific nonsense.
It’s also possible that eating outside presents little risk, and perhaps also that so long as there’s good ventilation with fresh air it’s equally safe to eat inside. Not that I’d bet my life on it without more research, but so far the patterns found through contact tracing suggest that virtually all infections have been through indoor air.
Duct cleaning and maintenance will put most of them out of business. It is not inexpensive.
Duct cleaning is unnecessary since the virus particles don’t stay viable very long. The Hunan bus study makes it clear that in recirculating air they can stay viable at least half an hour, but not much longer (since the last passenger to get infected got on half an hour after the one who was shedding particles got off).
How expensive it would be to eliminate the accumulation of virus particles in recirculated air will depend on the design of the HVAC system. Best case, there’s an option to choose between recirculated and fresh air. Worst case, there’s no exterior intake so it would require remodeling.
I’ve made some people seriously furious with me. It’s a cruise board and I’ve had the audacity to post info like the above. These people are willing to die, I suppose, to get back on a cruise ship. And here we are wondering if/when/how we’ll go to a freaking restaurant. Amazing.
In the Chang article that you posted here on May 7, people at table B were clearly infected by droplets from A1 being blown by the a/c fan over table A and then over table B. The people at table C may have been infected by droplets that managed to remain airborne on the return path to the a/c unit, or they may have been infected because the return airflow picked up new droplets from A1.
Air that is recirculated in airplanes passes through HEPA filters (I believe two stages) and is quite safe.
But: You don’t want to be downstream of a horizontal air current that is blowing air past an infected person who has coughed, sneezed, or talked loudly. Anywhere. Fans are just as bad as a/c units. Maybe worse. Note that no-one at tables D or E were infected, because there were no air currents from table A to those two tables (or anywhere else on that floor of the restaurant).
TY for having posted the referenced report by Lu, et. all here: Covid-19, and how to support the restaurant industry? - #191 by robert. In the report, one important finding was that there was no virus on the a/c unit. Virus-bearing droplets may have recirculated within the restaurant space, but neither they nor individual virus particles or clusters originated from the a/c unit itself. This is different in an important way from DD’s unfortunate experience with a mold-laden a/c in a test kitchen.
Also, there is a minimum number of virus particles necessary to infect. With bacteria, this is called the minimum number of “colony-forming units” (CFUs). One bacterial spore very rarely or never does it, although in principle it could, because a single spore by its lonely self is in fact a potential CFU. Similarly, while theoretically possible, it’s extremely unlikely to be infected by having inhaled fewer than some (unknown to me) minimum number of virus particles, alone, in solid clusters, or carried in droplets. Droplet/particulate density reduction through careful HVAC engineering, including filtering, are controls to limit CFU intake in an enclosed space.
As an aside with a suggestion, I used to do a great deal of business travel. If someone behind me or next to me on the airplane coughed or sneezed, even if there wasn’t anything “going around”, I would immediately hold my breath for as long as possible. That’s an easy defense to adopt, since coughing and sneezing are the primary mechanisms of covid transmission.
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It doesn’t matter if you’re downstream or upstream from the infected person, only whether you’re sharing recirculated air. Virus particles accumulate in the air over time, as shown by the person who was infected on the bus 30 minutes after the infected person got off. And as you said, the more virus particles, the more infectious the air is.
Asymptomatic carriers are a major source of infections, and they’re not coughing or sneezing.
Here it is, direct from the State of California and CalOSHA, the guidelines for restaurants to reopen.
I’ve skimmed them and I’m not sure how doable they are for many restaurants. Sorry, Robert, no mention of A/C but there are 2 bullet points pertaining to fresh air and air circulation
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There’s been some mention of restaurant air circulation in restaurants with wall-mounted a/c units, vis-à-vis virus spread. (E.g., a video on CBS news today.) These small a/c units probably have dust filters, but those filters are only intended to trap dust that would interfere with the a/c efficiency, as in a home furnace or central a/c. I think.
I did notice this (brief) comment in the CalOSHA guidelines:
“Consider installing portable high-efficiency air cleaners, upgrading the building’s air filters to the highest efficiency possible, and making other modifications to increase the quantity of outside air and ventilation in all working areas.”
Interesting to compare the CA with the WA guidelines:
Especially this:
9: “If the establishment offers table service, create a daily log of all customers and maintain that daily log for 30 days, including telephone/email contact information, and time in. This will facilitate any contact tracing that might need to occur.”