Ask The Brewmasters

Hi Jason,

Congratulations on having a CO₂ monitoring system.

May I offer a different perspective? You state you are interested in increasing the alarm set-point to reduce the frequency of alarms, when you might rather be concerned with reducing the excessive levels of CO₂ that are setting off alarms. 

Alarm set-points below the permissible exposure limit (PEL) give the employer a chance to act before employees are exposed above legal limits. An example is an alarm set-point of 20% of the explosive concentration of methane in air. You need to rectify the atmosphere or evacuate immediately to avoid being blown up, assuming the methane continues to accumulate.

Alarm set points above the PEL are often used when the results of overexposure aren't as catastrophic as blowing up the workplace. With CO₂, the thinking is that a worker could go over the all day average PEL of 5000 ppm for short periods, as long as the 8-hr time-weighted average (TWA), remains below 5000 ppm. But when an alarm sounds above 15000 or 30000 ppm, 1) what is the real concentration in the room? (A: we don't know unless we look at the display), 2) will this result in exceeding the 8-hr average? (A: we don't know unless we have integrated every measurement taken across those 8 hours), and 3) do I need to evacuate? (A: probably, if you're over 30000pm). Somewhere around 40000 ppm a worker may become impaired fast enough to interfere with self-evacuation. This value is called the IDLH (immediately detrimental to life or health). A trick for remembering IDLH is "I don't like it here!" Even so, all human bodies perform differently under exposure scenarios, so I prefer to be suspicious of the real protection afforded by the PEL or the IDLH.

Back to my original point, the primary good thing about an alarm going is off is it is telling you your process containment and exposure controls are inadequate. Don't fight the alarm, use it as a process control. An example: if the pressure gauge on a BBT rated for 15 psi was showing 40 psi, do you ask how to put more pressure into it or do you take immediate action to reduce pressure? 

CO₂ controls can be whatever means you invent to keep the CO₂ levels in check, as long as they don't make the problem worse for others. Some examples I've seen include:

• large shop fans (sometimes automated with CO₂ monitoring systems)
• opening up your more enclosed spaces during FV blowdown or turnover to promote dilution, could be as simple as opening windows or a dock door
• hard piping CO₂ exhaust to a safe outside area
• implementing CO₂ capture system
• substituting nitrogen where feasible
• optimizing CO₂ levels in filling and lidding, and so on. 

OSHA does not say CO₂ has to be managed a certain way. It says workers cannot be exposed above a workday average. To win the game, do what it takes to identify sources of fugitive CO₂ and manage its release to avoid overexposure. 

Cheers!

Thanks for the responses.  We do have several industrial fans positioned through the facility to keep air moving with a few installed in the exterior wall to keep steady air flowing.  We have additional air movers available to help move CO2 in any problem areas when an alarm does go off.  We're really doing as much as we can to keep fresh air moving through the facility.  I think the next logical step is to look at engineering fixes to vent tanks directly outside and things like that. 

I uploaded the specific information that is posted in the MBAA safety section that lists low level alarm at 15000 and high level alarm at 30000.  Perhaps that information should be changed if it's not accurate.  I'd like to follow what is accepted as best practices and was curious what levels others are using for their monitoring systems.

Hi Jason,

Congratulations on having a CO₂ monitoring system.

May I offer a different perspective? You state you are interested in increasing the alarm set-point to reduce the frequency of alarms, when you might rather be concerned with reducing the excessive levels of CO₂ that are setting off alarms. 

Alarm set-points below the permissible exposure limit (PEL) give the employer a chance to act before employees are exposed above legal limits. An example is an alarm set-point of 20% of the explosive concentration of methane in air. You need to rectify the atmosphere or evacuate immediately to avoid being blown up, assuming the methane continues to accumulate.

Alarm set points above the PEL are often used when the results of overexposure aren't as catastrophic as blowing up the workplace. With CO₂, the thinking is that a worker could go over the all day average PEL of 5000 ppm for short periods, as long as the 8-hr time-weighted average (TWA), remains below 5000 ppm. But when an alarm sounds above 15000 or 30000 ppm, 1) what is the real concentration in the room? (A: we don't know unless we look at the display), 2) will this result in exceeding the 8-hr average? (A: we don't know unless we have integrated every measurement taken across those 8 hours), and 3) do I need to evacuate? (A: probably, if you're over 30000pm). Somewhere around 40000 ppm a worker may become impaired fast enough to interfere with self-evacuation. This value is called the IDLH (immediately detrimental to life or health). A trick for remembering IDLH is "I don't like it here!" Even so, all human bodies perform differently under exposure scenarios, so I prefer to be suspicious of the real protection afforded by the PEL or the IDLH.

Back to my original point, the primary good thing about an alarm going is off is it is telling you your process containment and exposure controls are inadequate. Don't fight the alarm, use it as a process control. An example: if the pressure gauge on a BBT rated for 15 psi was showing 40 psi, do you ask how to put more pressure into it or do you take immediate action to reduce pressure? 

CO₂ controls can be whatever means you invent to keep the CO₂ levels in check, as long as they don't make the problem worse for others. Some examples I've seen include:

• large shop fans (sometimes automated with CO₂ monitoring systems)
• opening up your more enclosed spaces during FV blowdown or turnover to promote dilution, could be as simple as opening windows or a dock door
• hard piping CO₂ exhaust to a safe outside area
• implementing CO₂ capture system
• substituting nitrogen where feasible
• optimizing CO₂ levels in filling and lidding, and so on. 

OSHA does not say CO₂ has to be managed a certain way. It says workers cannot be exposed above a workday average. To win the game, do what it takes to identify sources of fugitive CO₂ and manage its release to avoid overexposure. 

Cheers!

Thanks for the responses.  We do have several industrial fans positioned through the facility to keep air moving with a few installed in the exterior wall to keep steady air flowing.  We have additional air movers available to help move CO2 in any problem areas when an alarm does go off.  We're really doing as much as we can to keep fresh air moving through the facility.  I think the next logical step is to look at engineering fixes to vent tanks directly outside and things like that. 

I uploaded the specific information that is posted in the MBAA safety section that lists low level alarm at 15000 and high level alarm at 30000.  Perhaps that information should be changed if it's not accurate.  I'd like to follow what is accepted as best practices and was curious what levels others are using for their monitoring systems.

Thanks for the responses.  We do have several industrial fans positioned through the facility to keep air moving with a few installed in the exterior wall to keep steady air flowing.  We have additional air movers available to help move CO2 in any problem areas when an alarm does go off.  We're really doing as much as we can to keep fresh air moving through the facility.  I think the next logical step is to look at engineering fixes to vent tanks directly outside and things like that. 

I uploaded the specific information that is posted in the MBAA safety section that lists low level alarm at 15000 and high level alarm at 30000.  Perhaps that information should be changed if it's not accurate.  I'd like to follow what is accepted as best practices and was curious what levels others are using for their monitoring systems.

That was my thought too.  The installation instructions were to install the sensors 12" off of the ground, which is what we did.  So it is obviously going to represent the very worst scenario and not be representative of what people would actually be exposed to while standing and working.

It needs to be stated while it makes sense to have monitors near the head region for most people (thinking for your shortest people), as I understand and logically surmise for full-scope safety measures,  you want to know the greatest concentration near the floor in case you go down for any reason--whether it be from CO2 or any other reason (e.g. trip and knock yourself unconscious, a medical condition, prolonged time doing something at the bottom of a tank like maintenance, etc.) so you don't die from something that you wouldn't have except for the fact there is too high of a concentration of CO2.  So what might just make you dizzy standing upright and might allow you to get out of the situation, but if you end up on the ground for whatever reason, you might be done for.  How safer than sorry do you want to be?

At one brewery I worked for, the city made us put in automatic fans and louvers tied into our CO2 monitoring system due to the potential output from our 100 bbl tanks.  Only once did I ever see an alarm go off, but periodically saw the louvers open and fan turn on.  So as long as no governing body based on your location says others, you might be able to not have alarms until it gets to more critical levels after a certain time.  I don't remember if our louvers were set to up first at a certain level, and if the too much time elapsed without dropping below a certain set point, the fans would kick on, but I like that idea.  That same brewery when they opened, the plan was to get to 10,000 bbl as soon as possible and started with only one brewer.  One day while manually dry hopping a 100 on a ladder towards the end of fermentation, he passed out on the ladder over the tank.  Luckily it wasn't for long and he didn't fall the 25 or so feet.  After that dry hopping became a two-person task. Even with a good monitoring and venting system, it failed in this situation.

That was my thought too.  The installation instructions were to install the sensors 12" off of the ground, which is what we did.  So it is obviously going to represent the very worst scenario and not be representative of what people would actually be exposed to while standing and working.

Jason, I read your initial question as an 'Alarm Function' Concern more than a 'Safe Level' Concern. To Matt's point, having a low-level alarm of 15,000-ppm gives plenty of time to mitigate the issue before it reaches its full hazard potential. Whereas a low-level alarm of 5,000-ppm may initiate monitoring towards a PEL. Is there a clear reaction plan in place, or further monitoring when the 5,000-ppm threshold is crossed? Maybe once the alarm is activated, hourly monitoring could be conducted. That reaction plan may reduce the likelihood of a 'nuisance alarm' being ignored. Someone else mentioned draeger tubes for testing exposure over longer periods of time. These can be a reference point if you're concerned how the monitors represent working conditions. Do you have only the Low- and High-level alarms? Do you have a High-High option (5,000 = monitor; 15,000 = mitigate; and 30,000 = evacuate)? I'd be reluctant to change the settings if frequently cresting the 5,000 ppm mark.  

I would note that carbon dioxide is listed as both an asphyxiant and toxic gas by the USDA and NIH. 

Elevated CO2 concentration used to be the #1 cause of fatal accidents in wine cellars in Germany, before CO2 monitors were available. Cellar masters used a lit candle as a simple detector. Since CO2 is heavier than air it settles at the floor level and that's were you find the highest concentrations. You could capture the CO2 in an alkali trap, but that has other hazards associated with it and venting to the outside might be a safer and more economical. Some German breweries used to recapture the CO2 to later carbonate the beer with it, as the addition of fresh CO2 would have been against the German Reinheitsgebot... 

Elevated CO2 concentration used to be the #1 cause of fatal accidents in wine cellars in Germany, before CO2 monitors were available. Cellar masters used a lit candle as a simple detector. Since CO2 is heavier than air it settles at the floor level and that's were you find the highest concentrations. You could capture the CO2 in an alkali trap, but that has other hazards associated with it and venting to the outside might be a safer and more economical. Some German breweries used to recapture the CO2 to later carbonate the beer with it, as the addition of fresh CO2 would have been against the German Reinheitsgebot...