Charcoal Braziers and Safety

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pedant
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Thu Apr 05, 2018 10:36 pm

it is for sure a real concern. from the jstage article i linked to above:
Jun OJIMA wrote:Every year in Japan, a number of cooks, waiters and waitresses are poisoned in the kitchen or semi-enclosed spaces by CO generated by burning charcoal.
Baisao wrote:
Thu Apr 05, 2018 10:05 am
pedant wrote:
Thu Apr 05, 2018 2:44 am
Then i found an article with an actual experimental approach. they looked at binchotan and came up with this figure:
"Theoretical ventilation requirements for charcoals to prevent CO poisoning are estimated to be 41.2–55.6 m3/h/kW." 3
Thank you, Pedant. I appreciate a more scientific approach to this. Based on that last formula, it looks like a 4x4x3 meter room would be safe from poisoning for at least an hour. (Is this correct?) That's a pretty small room and I wouldn't begin to consider using a brazier in a room so small without a lot of ventilation. If this is correct, it would help explain how these were frequently used in Japanese homes.
room size doesn't really factor into that formula. that ventilation rate is for a fume hood placed right by the stove.
table 2 in that paper is really nice though and gives their experimental data for CO generation rate for 5 different binchotan charcoals.
the highest recorded test gave 216 mL/min/kW CO. going back to my stated requirement (bring a liter of water from room temp to boiling in 15 minutes), that's 0.371 kW. so such a stove would generate 80.1 mL CO / min.

to get CO concentration (volumetric ppm), you do:

CO concentration in ppm = 80.1 mL/min * (stove runtime in min) / (volume of room in mL) * 10-6

so running such a stove for 15 minutes in a 4m*4m*3m room, you get 25 ppm CO.
that's for a completely sealed room with no ventilation, and it assumes that the air in the room is homogenous (running a fan or something).
from the source in my above post, it says that 25ppm is "Max TWA Exposure for 8 hour work-day (ACGIH)" and has "Possible health effects with long-term exposure."

that's much better than my worst-case scenario calculation which assumed that all of the carbon in the charcoal was converted to CO.

i'd still run a fan (not pointing right at the stove lol), open up the doors and windows, and plug in a CO alarm nearby.
fire extinguisher couldn't hurt either. :lol:
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Baisao
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Fri Apr 06, 2018 9:53 am

CWarren wrote:
Thu Apr 05, 2018 9:19 pm
I only light my charcoal outdoors so I’m no authority on indoor use. My plan was to place an indoor hood in my tea room at some point for proper ventilation but given the time it takes to get to ember there is much more to worry about than just smoke even with the “smokeless” Japanese varieties. I’d only consider it after going to ember and then bringing the coals indoors under vent or by a large open window and only in a large room, (my tea room is about 12’ x 20’). I use bamboo, olive pit, sumi and binchotan. I would advise against indoor use with bird owners as it can have fatal consequences, (incense and candles as well).
Sage advice based upon experience. Thank you!

I started the smokeless rambutan sumi last night under the broiler per a method mentioned on Amazon and noticed that it was smoking more than I expected it to. This also meant that it was releasing more CO than I expected it to. That's when I decided to stop it and move the process to outdoors using a chimney starter. It took 30 min for a small bofura to come to a boil. Not exactly convenient when an oolong can change flavor after sitting for a mere 20 minutes.
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Baisao
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Fri Apr 06, 2018 9:59 am

pedant wrote:
Thu Apr 05, 2018 10:36 pm
room size doesn't really factor into that formula. that ventilation rate is for a fume hood placed right by the stove.
table 2 in that paper is really nice though and gives their experimental data for CO generation rate for 5 different binchotan charcoals.
the highest recorded test gave 216 mL/min/kW CO. going back to my stated requirement (bring a liter of water from room temp to boiling in 15 minutes), that's 0.371 kW. so such a stove would generate 80.1 mL CO / min.

to get CO concentration (volumetric ppm), you do:

CO concentration in ppm = 80.1 mL/min * (stove runtime in min) / (volume of room in mL) * 10-6

so running such a stove for 15 minutes in a 4m*4m*3m room, you get 25 ppm CO.
that's for a completely sealed room with no ventilation, and it assumes that the air in the room is homogenous (running a fan or something).
from the source in my above post, it says that 25ppm is "Max TWA Exposure for 8 hour work-day (ACGIH)" and has "Possible health effects with long-term exposure."


that's much better than my worst-case scenario calculation which assumed that all of the carbon in the charcoal was converted to CO.

i'd still run a fan (not pointing right at the stove lol), open up the doors and windows, and plug in a CO alarm nearby.
fire extinguisher couldn't hurt either. :lol:
Highlighted above for emphasis.

Thank you, Pedant for the calculations you used and for presenting the findings in a way that's consumable for those of us who are mathematically challenged. This could save lives.
.m.
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Fri Apr 06, 2018 12:35 pm

CWarren wrote:
Thu Apr 05, 2018 9:19 pm
I would advise against indoor use with bird owners as it can have fatal consequences, (incense and candles as well).
Very good point. Perhaps valid with respect to other animals too. Back in the days they used canaries in coal mines. Those poor creatures. The advice might have been given the other way back then: against indoor use for people not owning a bird.
.m.
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Fri Apr 06, 2018 12:42 pm

I remember a post by Petr Novak on his blog a couple years ago about washing charcoal to reduce smoke. Not sure what the principle behind was. Must have somehow improved the combustion.
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Baisao
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Fri Apr 06, 2018 2:39 pm

.m. wrote:
Fri Apr 06, 2018 12:42 pm
I remember a post by Petr Novak on his blog a couple years ago about washing charcoal to reduce smoke. Not sure what the principle behind was. Must have somehow improved the combustion.
My understanding is that it reduces smoke and prevents it from throwing sparks at the beginning, as it is being lit. This would not affect the amount of CO the lit coals produce once they have been put into service. Washing the dust off of coal is a common practice in chanoyu.

I am curious to read his blog posting and will search for it tonight.
.m.
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Sat Apr 07, 2018 8:56 am

Baisao wrote:
Fri Apr 06, 2018 2:39 pm
.m. wrote:
Fri Apr 06, 2018 12:42 pm
I remember a post by Petr Novak on his blog a couple years ago about washing charcoal to reduce smoke. Not sure what the principle behind was. Must have somehow improved the combustion.
My understanding is that it reduces smoke and prevents it from throwing sparks at the beginning, as it is being lit. This would not affect the amount of CO the lit coals produce once they have been put into service. Washing the dust off of coal is a common practice in chanoyu.

I am curious to read his blog posting and will search for it tonight.
Yes it makes sense that it would make a difference mainly at the beginning when the coal is being lit up.
The amount of CO produced should depend on the quality of the combustion which is determined mainly by the quality of the fuel and the design of the stove. For example "rocket stoves" are said to burn more cleanly than normal stoves. The way the charcoal is stacked within the brazier should also make some difference. But, i wouldn't be able to say anything beyond these obvious considerations.
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Manttea
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Sat Apr 07, 2018 2:18 pm

Baisao wrote:
Fri Apr 06, 2018 9:53 am
CWarren wrote:
Thu Apr 05, 2018 9:19 pm
I only light my charcoal outdoors so I’m no authority on indoor use. My plan was to place an indoor hood in my tea room at some point for proper ventilation but given the time it takes to get to ember there is much more to worry about than just smoke even with the “smokeless” Japanese varieties. I’d only consider it after going to ember and then bringing the coals indoors under vent or by a large open window and only in a large room, (my tea room is about 12’ x 20’). I use bamboo, olive pit, sumi and binchotan. I would advise against indoor use with bird owners as it can have fatal consequences, (incense and candles as well).
Sage advice based upon experience. Thank you!

I started the smokeless rambutan sumi last night under the broiler per a method mentioned on Amazon and noticed that it was smoking more than I expected it to. This also meant that it was releasing more CO than I expected it to. That's when I decided to stop it and move the process to outdoors using a chimney starter. It took 30 min for a small bofura to come to a boil. Not exactly convenient when an oolong can change flavor after sitting for a mere 20 minutes.
This is my experience as well, it really takes a while every time you fill it with cooler water. I'd be tempted to bring the temperature up if they weren't so prone to cracking.
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Baisao
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Sat Apr 07, 2018 8:08 pm

Manttea wrote:
Sat Apr 07, 2018 2:18 pm
This is my experience as well, it really takes a while every time you fill it with cooler water. I'd be tempted to bring the temperature up if they weren't so prone to cracking.
The fellow who made my kettle also makes tea with GongFu. He has multiple kettles going in the photos I have seen of him. Usually two in the background and a smaller one near him. He refills the smaller one with hot water from the larger kettles.

Also, looking at photos a friend took of a gathering of tea masters I can see that most had two kettles: one large one behind them and a smaller one on or near their table. I heard from my friend that they fill the smaller kettles from the large ones so there is no delay.
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Manttea
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Sun Apr 08, 2018 12:58 am

Baisao wrote:
Sat Apr 07, 2018 8:08 pm
Manttea wrote:
Sat Apr 07, 2018 2:18 pm
This is my experience as well, it really takes a while every time you fill it with cooler water. I'd be tempted to bring the temperature up if they weren't so prone to cracking.
The fellow who made my kettle also makes tea with GongFu. He has multiple kettles going in the photos I have seen of him. Usually two in the background and a smaller one near him. He refills the smaller one with hot water from the larger kettles.

Also, looking at photos a friend took of a gathering of tea masters I can see that most had two kettles: one large one behind them and a smaller one on or near their table. I heard from my friend that they fill the smaller kettles from the large ones so there is no delay.
I'm definitely doing this next time. The wait is just jars the experience
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Baisao
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Sun Apr 08, 2018 1:31 am

Manttea wrote:
Sun Apr 08, 2018 12:58 am
I'm definitely doing this next time. The wait is just jars the experience
Ditto. By the time it takes a kettle to reboil over charcoal the tea will have changed. Having hot water on backup, even if one is staged from an electric kettle, seems ideal.

I was surprised this evening by how big a difference a quality clay kettle made to the flavor of the tea when compared to water directly from a stainless steel kettle.

In the case of my kettle, the water was smoother, less edgy, and slightly sweeter. I went back to the stainless steel kettle during the same session and the water was harsh and edgy. The difference was not subtle.

So there’s value in using clay kettles even if we’re unable to use charcoal for whatever reason.
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