Bars and Taverns: Late Hours, Beer Lines and CO2 Cellars

Why this matters

Safety first, before anything else on this card. If a CO2 detector is alarming, if your personal monitor reads high, or if anyone in a cellar or walk-in cooler is dizzy, short of breath, has a sudden headache or is confused, everyone leaves the space immediately and nobody goes back in to help or to look. Call 911 if anyone is symptomatic or down. Ventilate only from outside the space (opening an exterior cellar door or hatch you can reach without entering), tell the bar's manager, and do not re-enter until the source is stopped and a reading at the floor of the space is back under 5,000 ppm and falling. Carbon dioxide has no smell, and a person who goes in after a collapsed coworker becomes the second victim.

A bar looks like a small restaurant to a tech who does restaurants. Two things make it different. It keeps hours that push almost all service work into the morning, when the person who knows the building is asleep. And it stores beverage gas, usually CO2, sometimes blended with nitrogen, in a below-grade cellar or a walk-in cooler, the two places a heavier-than-air gas collects. Most bar calls are uneventful. The ones that are not tend to involve both.

The hours and who is there

Bars commonly close at 2 am, sometimes later where local law allows, and the staff are cleaning until an hour after that. Many open at 11 am for lunch; many others not until late afternoon. That leaves late morning as the realistic window for planned work, and it creates two problems.

The person who can authorize anything may not be there. The morning crew may be a single prep cook or a cleaner. A walk-in repair that turns into a compressor job needs the owner or the general manager, who closed the bar seven hours ago. Get the decision-maker's number and agreement to be called when the call is booked. See related: Who Can Actually Authorize Work in a Business.

Access is an alarm and keys question. An empty bar at 9 am is a monitored building with cash in it. See related: Keys, Alarm Codes and Access Cards at a Business.

The other side of late hours: a bar's emergency calls tend to come at 6 pm on a Friday, when the walk-in full of kegs and garnish warms up during the busiest night of the week. Product tolerance in a keg cooler is mostly about beer quality and the food stored alongside it, and the food clock is the one with a health rule behind it.

What a CO2 cellar does, and where the gas goes

Most draft systems push beer from the keg to the tap with CO2 from high-pressure cylinders, or from a bulk insulated liquid CO2 tank refilled by a supplier. Stouts and long-draw systems often use a CO2 and nitrogen blend. Long-draw systems, where the kegs are far from the taps, run the beer lines in an insulated bundle called a trunk line cooled by a glycol chiller, often called a power pack.

CO2 is about one and a half times as dense as air, so a leak sinks and pools along the floor, in a stairwell foot, a floor drain pit or the bottom of a walk-in cooler with its door closed. A cellar that was sealed overnight with a slow leak can hold a layer of high CO2 at knee height while the air at head height reads near normal.

 BAR (street level)        taps
 ---------------------------|--------------------
 CELLAR (below grade)       | beer lines and
                            | trunk line up chase
  stair   +-----------------|---+
  from    | WALK-IN KEG COOLER  |   CO2 cylinders,
  bar     | kegs, couplers,     |   chained upright,
   |      | gas lines           |   regulators on
   v      |                     |   the manifold
  ........|.....................|................
  LOW POINT: floor of walk-in, stair foot, drain
  pit. CO2 pools here. Test here first, low.

Two physical facts to carry.

CO2 is toxic in its own right, well before it starves you of oxygen. OSHA's permissible exposure limit for CO2 is 5,000 ppm as an 8-hour average (29 CFR 1910.1000, Table Z-1), and NIOSH lists 40,000 ppm as immediately dangerous to life or health. An oxygen meter alone does not protect you. See the worked example for why.

Nitrogen in a blended system is a different hazard. It does not cause the headache and air hunger that warn of CO2. It simply displaces oxygen, and a person can lose consciousness without feeling short of breath. Where a blend is in use, an oxygen reading matters as much as a CO2 reading.

What the fire code may require

Because of fatal incidents in restaurants and bars, the International Fire Code added a section on CO2 systems used in beverage dispensing (Section 5307 in the 2015, 2018 and 2021 editions), which applies to systems holding more than 100 pounds of CO2 and requires gas detection with alarms in the rooms where CO2 can accumulate, among other provisions. It binds the business where your jurisdiction has adopted one of those editions, and some states and cities have added their own rules. Many bars now have a wall-mounted CO2 detector near the cellar or walk-in. A tech should know where it is, and should never silence, unplug or move it.

The fire code, as adopted, also generally requires compressed gas cylinders to be secured against falling, which is why the cylinders in the sketch are chained. A cylinder knocked over with its valve sheared becomes a projectile.

Never disturb the draft system

The draft system belongs to the bar and to whoever services it, usually a draft technician or line-cleaning service. A refrigeration, plumbing or electrical tech working nearby leaves every part of it alone:

• Do not close, open or adjust CO2 or blended-gas regulators, even to stop a hiss. Report the hiss.
• Do not disconnect couplers from kegs or move kegs to get at a coil or a drain. Ask the bar's staff to move them.
• Do not kink, cut, unclip or re-route beer lines or gas lines, including to slide a ladder or a new evaporator in.
• Do not unplug or switch off the glycol power pack to free a receptacle or quiet the room. A warm trunk line foams every tap upstairs at opening.
• Do not open the lines for cleaning or run water through them. Line cleaning uses specific chemicals and is the draft service's work.

If your repair truly needs the draft system shut down, the bar arranges that with its draft service before you arrive.

Worked example: a 9:30 am walk-in call

A refrigeration tech arrives at 9:30 am at a tavern for a keg cooler that the closing manager reported running warm. The cellar is below grade with one interior stair from the bar. The walk-in door has been closed since 3 am. The bar's wall CO2 detector is at head height on the cellar side of the stair, and it is quiet.

At the stair foot, the tech's personal CO2 monitor, clipped low on the belt, reads 1,800 ppm. Normal outdoor air is around 420 ppm, so the cellar is already elevated, but the reading is under 5,000 ppm. The tech notes it and approaches the walk-in.

At the walk-in door, opened a crack, the monitor climbs to 12,000 ppm within a few seconds. The tech closes the door, leaves the cellar by the stair, and calls the manager. No one is symptomatic, so no 911 call, but the bar's own detector, mounted at head height outside the walk-in, never alarmed. That is the point of the low monitor.

Why an oxygen meter would have missed it. CO2 at 12,000 ppm is 1.2 percent of the air. If it displaces air evenly, oxygen falls from 20.9 percent to about 20.9 times 0.988, which is 20.6 percent, well above the 19.5 percent that OSHA treats as oxygen-deficient. Yet 12,000 ppm is 2.4 times the 5,000 ppm limit (12,000 divided by 5,000). Working backward, CO2 alone would have to reach about 6.7 percent, or 67,000 ppm, to push oxygen down to 19.5 percent (1 minus 19.5 divided by 20.9 is 0.067), and that is far past the 40,000 ppm IDLH level. On a pure CO2 leak, by the time an oxygen meter alarms, the CO2 has already been dangerous for a long time.

What happened next. The manager calls the draft service, which finds a leaking coupler on a keg in the walk-in, a slow leak that ran all night into a closed box. The manager opens the cellar's exterior hatch from the sidewalk. The draft tech, carrying their own monitor, replaces the coupler gasket. Forty minutes later, the reading at the walk-in floor is 3,900 ppm and falling, under the 5,000 ppm re-entry line and moving the right way, and the refrigeration tech goes back in with the monitor still on and the walk-in door propped open.

The refrigeration problem was real too. The evaporator coil was iced over from a failed defrost timer. While the walk-in was warming, the kegs were fine for beer quality over a morning, but a pan of cut lemons and a tub of house-made dip stored on the top shelf were TCS food above 41 F for an unknown time, and the manager discarded them.

What changes the answer. On a blended CO2 and nitrogen system, the same leak would have lowered oxygen with less CO2 warning, and the tech's re-entry would also need an oxygen reading of at least 19.5 percent at the floor. If the walk-in had a bulk liquid CO2 tank rather than cylinders, the supplier, not the draft service, would be the first call for a leak at the tank.

Verifying before you leave a bar cellar

• The CO2 reading at the walk-in floor and the stair foot, written on the ticket with the time.
• Every draft component exactly as you found it, with nothing you moved left out of place.
• The bar's CO2 detector powered and in place.
• Walk-in air temperature, the staff's own product readings, and a note of anything the manager discarded and why.
• The manager or owner told about any gas reading above normal, even if the source was found and fixed, because a bar with one leaking coupler often has another.

References

• 29 CFR 1910.1000, Table Z-1 (CO2 permissible exposure limit) and 29 CFR 1910.146 (oxygen-deficient atmosphere definition)
• NIOSH Pocket Guide to Chemical Hazards, carbon dioxide (IDLH and recommended limits)
• International Fire Code Section 5307, carbon dioxide systems used in beverage dispensing, in the edition adopted by your jurisdiction
• See related: Working in Commercial Kitchens Reference
• See related: How to Work a Restaurant After Close and Leave It Ready to Open