Any school shop teachers here? Questions about upcoming year.

[Evin Moore]

If there is a thread already about this, I'd appreciate a link. Also, wasn't sure which forum to post in.

I'm director of a college woodshop and am quickly approaching the day of face to face contact with students.
Lecture classes will be taught completely online, but studio classes will still be in-person, and many students rely on the shop for their major practice.
Ours is a facility much like the campus library, open to all enrolled students, faculty and staff.

We are, of course, told to adhere to CDC guidelines regarding masks, social distancing, hand washing, etc. I am wondering how others in the same position are planning to manage traffic through the shop. So many projects require the use of multiple machines and tools, and not always in a convenient sequence. Student projects that come into the shop are highly individual.

I have more specific concerns regarding dust, air circulation and how to disinfect cast iron table tops without rusting, and disinfecting hand and power tools between users.

Starting to lose a lot of sleep, here. Could use some guidance, or at least moral support.
Thanks.

[Bill Dufour]

I think a wipe down with paint thinner would sterilize cast iron. Or 100% alcohol would not cause rust. The virus is contained inside a fat layer so any fat solvent should do the trick. Not sure if machine oil will do that or not. Three hours on dry unfinished wood or paper will dry it out..dead.
Bill D.

[Charlie Velasquez]

The CDC guidelines are nice, but they deal with what the people should be doing to reduce risk. They don’t address the nuts and bolts of what the building should be doing to reduce the spread. The American Society of Heating, Refrigeration and Air-conditioning Engineers is the organization that gives guidance on air circulation. Their guideline for covid could be expensive for your institution in KC MO where it gets hot in August and September and cold in January and February.

Normally the hvac system is supposed to bring in 15cu.ft.per minute per student of outside fresh air, about 350cfm per classroom. So if your air handlers can blow say 900 cfm it will pull 350cf of outside fresh air and 550cf of recirculated inside air, mix it together and blow it back into the room. Your system only has to condition that 350cf of outside air and just a tiny bit of that 550cf of inside air.

But studies have shown hvac systems can keep moisture droplets air borne longer and recirculate them in the room.
ASHRAE guideline is no recirculated air at all, 100% outside air, with dampers fully open (and exhausts running). The idea is to blow all the possible contaminants outside as quickly as possible. So instead of paying to heat or cool 350 cfm, you have to pay to heat or cool 900cfm, blowing it outside as fast as you can condition it. In effect, you are trying to air condition the outside.

They have other guidelines wrt filters (max your system can handle up to merv 13-14), purging air overnight, shutting down cross contamination equipment (energy recovery units). No one ever talks about this, but it is a very real cost. In my latitude, about 41°N, I would guess it would double the costs of hvac.

[Brian Elfert]

My employer is/was bringing in 100% outside air at night that is unconditioned due to COVID. The building is designed for HVAC year round like most newer buildings so it is like a swamp in the morning. It takes most of the day for the air conditioning to catch up. I am glad I am working from home for the next three weeks and can control my own HVAC to stay cool.

[Brian Elfert]

I think a wipe down with paint thinner would sterilize cast iron. Or 100% alcohol would not cause rust. The virus is contained inside a fat layer so any fat solvent should do the trick. Not sure if machine oil will do that or not. Three hours on dry unfinished wood or paper will dry it out..dead.


They say that 100% alcohol won't kill the virus and that the alcohol needs to be diluted.

[Bill Dufour]

They say that 100% alcohol won't kill the virus and that the alcohol needs to be diluted.

I think that is a wipe down problem of too quick evaporation. flooding it and maintaining it damp for 20 seconds should do it on horizontal surfaces.
I suppose waving a propane torch over the metal would do it as well with minimal paint damage.
Bil lD

[Charlie Velasquez]

My employer is/was bringing in 100% outside air at night that is unconditioned due to COVID. The building is designed for HVAC year round like most newer buildings so it is like a swamp in the morning. It takes most of the day for the air conditioning to catch up. I am glad I am working from home for the next three weeks and can control my own HVAC to stay cool.

This time of the year our schools do a test run of all the hvac to make sure it runs as expected after the summer shutdown.
Usually during the school year we shut the buildings‘ hvac down when the kids leave and the buildings only lose a few degrees overnight. To completely purge the air you have to run the air handlers all night. By the next morning the building is at ambient outside temperature. Instead of running the furnace/compressors for 30 minutes in the morning to get back to temp, as you noted, they had to start about 4 hours early; a school building, desks, books, file cabinets, etc., have a lot of mass. To be fair, we were in a mild heat wave where the overnight low temp was about 79°, normally we could expect lows to be about 70° in September. But in the winter, we can expect the lows to be regularly in the low 20s with maybe even some negatives. To purge that air overnight we would need to run the boilers 24 hrs a day.

[Aaron Rosenthal]

I'm involved in a large public building, not like a school but with the same issues.
I've learned that the air filters we use are not up to filtering out anything the size of Corona virus droplets, and our HVAC person is adding fresh air to the re circulation mix. I honestly don't know what that will achieve.
We can clean surfaces with bleach products, but even with mandatory masks, I can't see how transmission can be avoided.

[Nicholas Lawrence]

I think that is a wipe down problem of too quick evaporation. flooding it and maintaining it damp for 20 seconds should do it on horizontal surfaces.
I suppose waving a propane torch over the metal would do it as well with minimal paint damage.
Bil lD

If science has changed again and Alcohol is no longer any good, use bleach.

I don't think you need to burn the shop down.

To answer the question about changing the air mix: bringing in outside air helps because it is not just exposure to the virus that matters, but viral load. Your immune system can handle a certain number of virus particles, but once it gets above a certain threshold the immune system cannot keep up and you get sick.

If someone in the building is infected, they are breathing particles into the air. When the air is recirculated, you breath in however many of those particles are in the air. The additional fresh air dilutes things, reducing the viral load and making it less likely you will get sick.

One of those "every little bit helps" kind of things.

[Evin Moore]

Thanks to everyone contributing to this thread.
The ASHRAE site is a valuable resource; that, along with the other comments, has given me some context from which to consider my next moves.

[Rod Sheridan]

Evin since you’re dealing with the safety of the public, your school should hire a licensed Engineer to provide some options.

You don’t want to expose yourself to the potential liability......Regards, Rod.

[Bruce King]

Reminds me of 9th grade shop class.... Huge machines but only one of each type. The only student that already knew how to build things commandeered the teacher to help him hog the machines and the rest of us cut Pine with hand saws, still pissed off. And to make it worse the day my Dad finally came to pickup my “book case” I was not there because I skipped the whole day.

[Malcolm Schweizer]

I teach woodworking at www.mybrothersworkshop.org We have a very small number of cases here, but taking precautions just like the states. The students MUST wear masks at all times, properly worn. Hand sanitizer is used religiously and kept in stations. I see no need to sanitize machinery. The tables are cleaned daily with denatured alcohol, but that's not because of COVID-- that's because of chicken poop. (See my post about chicken traps needed) We shut down the shop at the start of things and our cafe' and bakery started making meals for people shut in due to COVID19. WE delivered over 30,000 meals! The shop folks became delivery drivers. The shop is now back running, with afore-mentioned precautions, as well as social distancing. The shop is open-air, i.e. basically a pole building open at two ends.

I am very concerned now because tourism has opened up and planes are coming in full of people. Cruise ships are not running, and that is good, because we get 10,000 to 20,000 cruise ship passengers a day during high season. Our hospital can't handle very many patients.