The number of breweries in the United States is on the rise. Last year (2018), the number of breweries in the US cracked 7,000. This year, another 1,000 are expected to open1. Breweries, and the increasingly popular brewpub (a restaurant that sells beer brewed on site), challenge the professional world as they introduce fire and health hazards. To protect brewhouse occupants, designers and regulators must understand brewing operations and the hazards they create.
A typical brewery involves the following operations:
- Create malt
- Mill malt
- Mash grist
- Lauter mash
- Boil wort
- Whirlpool hopped wort
- Cool wort
- Ferment wort
- Adjust beer (add CO2, filter, etc.)
- Package and store beer
Breweries can create malt or buy it from suppliers. To create malt, barley (or another grain) is steeped, germinated, and dried in a kiln. The hazards associated with these processes are limited to moderate. The kiln must be installed and operated per manufacturer’s specifications. The International Mechanical Code (IMC) should be consulted to provide ventilation, exhaust, and make-up air. Depending on kiln design and heat source, additional requirements may exist for safe operation, including active (suppression) and passive (hourly rated walls) protection.
Once malt is obtained, it is wet or dry milled to create grist (cracked malted barley). Wet milling is an increasingly popular technique that eliminates most hazards. Dry milling can create a deflagration hazard if not properly addressed. A deflagration is the rapid propagation of a flame front through a fuel-air mixture at subsonic speed. Combustible particulates having an equivalent diameter less than 420 microns can deflagrate when suspended in air at correct concentrations2. Prior to installing a dry mill, product literature should be evaluated to determine appropriate safeguards. The following safeguards negate milling hazards:
- Select a mill that creates particulates large enough to not produce a deflagration.
- Use a mill of metal construction.
- Equip the mill with a dust-ignition-proof (Class 2) motor. This should not be confused with an explosion-proof (Class 1) motor. Per the National Electric Code (NFPA 70), explosion-proof equipment and wiring shall not be required and shall not be acceptable in Class 2 locations unless also identified for such locations.
- Equip the mill hopper with a lid to prevent the dispersal of fine particles.
- Enclose the mill room to prevent the accumulation of dust throughout the brewery.
- Create a protocol to regularly clean walls, floors, and horizontal surfaces (equipment, beams, ducts, etc.) at a frequency that prohibits a layer of dust thicker than 1/32-inch. Such a thickness creates a deflagration hazard per the Standard for the Prevention of Fire and Dust Explosions from the Manufacturing, Processing, and Handling of Combustible Particulate Solids (NFPA 654).
- Where dust hazards exist, vacuum cleaners shall meet Class 2 hazardous location requirements, in accordance with the Fire Code (NFPA 1).
The grist is transferred to a vessel known as a mash tun. Here, the cracked malted barley is mixed with hot water to break down its starches into simple sugars. The grist-water mixture is known as a mash. The hazards associated with this process are limited. However, a heat source is used to create the hot water. Excluding smaller, non-fossil fuel fired equipment, the International Building Code (IBC) and the Life Safety Code (NFPA 101) require areas housing heat producing appliances to be protected by 1-hour fire rated construction, an automatic sprinkler system, or both. Specific applications must be evaluated to determine the appropriate safeguard.
The mash is transferred to a vessel known as a lauter tun. The vessel has a screened false bottom that filters the mash’s barley from its sweetened liquid. The remaining liquid is known as wort. This process is not hazardous.
The wort is transferred to a kettle where it is boiled. Hops are added to the wort for taste and aroma. Yet again, heat sources must be evaluated to determine appropriate safeguards.
The hopped wort is placed in a vessel known as a whirlpool. The whirlpool separates the trub (barley and hop particles) from the wort. This process is not hazardous.
Multiple methods are used to cool the wort. The wort can go through a heat exchanger while being transferred to a fermentation vessel. Or, the fermentation vessel can be jacketed to dissipate heat. Propylene glycol (a refrigerant) is commonly used in the cooling process. It is an irritant and a Class IIIB combustible liquid. However, large quantities of the refrigerant are allowed in such closed-use systems. According to the IBC, quantities of Class IIIB combustible liquids are not limited in buildings equipped with an automatic sprinkler system that is installed in accordance with the Standard for the Installation of Sprinkler Systems (NFPA 13).
Once in the fermentation vessel, yeast is added to the wort. The yeast consumes the wort’s simple sugars to produce ethyl alcohol (ethanol) and carbon dioxide (CO2). Beers generally contain less than 16% alcohol by volume (ABV). A beer’s flashpoint depends on its concentration of alcohol. According to the IBC, a liquid’s flash point is the minimum temperature at which the liquid will give off enough vapors to form an ignitable mixture with air near the surface or in a container but will not sustain combustion. Above 3.5% ABV, beers generally have a flashpoint between 100 and 200 degrees. Liquids having a closed cup flash point at or above 100 degrees Fahrenheit and below 140 degrees Fahrenheit are Class II combustible liquids. Liquids having a closed cup flash point at or above 140 degrees Fahrenheit and below 200 degrees Fahrenheit are Class IIIA combustible liquids. Thus, beers are generally Class II or Class IIIA combustibles liquids. However, per Section 306.3 in IBC-2015, the manufacturing or packaging of beverages, up to and including 16% ABV, does not create a significant fire hazard.
As mentioned, carbon dioxide (CO2) is generated during fermentation. After fermentation, beer is typically carbonated by force (CO2 is injected into beer-filled containers at a high pressure, forcing the beer to absorb CO2). Carbon dioxide (CO2) is a colorless, odorless gas that occurs naturally in earth’s atmosphere (about .04% by volume). It is not a fire hazard. However, it dilutes oxygen. At higher levels, CO2 can cause dizziness, loss of consciousness, and death. Per OSHA, the permissible exposure limit (PEL) for CO2 is 5,000 PPM (0.5% by volume) over an 8-hour day. Thus, CO2 monitoring and ventilation are important safeguards to protect brewery occupants.
Breweries involve the manufacturing and packaging of goods. Thus, they are classified as factory use groups. As mentioned, the manufacturing or packaging of beverages up to and including 16% ABV does not create a significant fire hazard. Such processes create low-hazard factory (F-2) use groups. Processes that include the manufacturing or packaging of beverages over 16% ABV create moderate-hazard factory (F-1) use groups. Per IBC commentary, moderate-hazard factory (F-1) use groups are also created when more than one layer of combustible material is used to package or finish low-hazard products.
Brewery stock areas are classified as moderate-hazard storage (S-1) or low-hazard storage (S-2) use groups, depending on the combustibility of materials stored. Per Section 311.3 in NFPA 101-2015, beverages up to and including 16% ABV (in metal, glass or ceramic containers) are considered low hazard. It’s acceptable for low-hazard products to be stored in combustible materials if the quantity of packaging is kept to insignificant levels. Per IBC commentary, low-hazard products stored in one layer of combustible packaging create low-hazard storage (S-2) use groups. For example, drinks less than or equal to 16% ABV in glass bottles packaged in pressed paper boxes create low-hazard storage (S-2) use groups. Moderate hazard storage (S-1) use groups are created when low-hazard contents are stored in more than one layer of combustible packaging.
From the cracking of malted barley to the last fermentation, the production of beer is a multistep process that creates fire and health hazards. By understanding brewing operations, the severity of hazards can be reduced with appropriate safeguards. Thus, it is important for designers and regulators to understand such operations to protect the increasing number of occupants in brewhouses.
Written By: Mark R. Richards, PE
Image taken from: https://www.gooseisland.com/international-locations/toronto-brewhouse
1 Snider, Mike. “The Year in Beer: Cheers, There’s More than 7,000 Breweries Operating in the US.” USA Today, Gannett Satellite Information Network, 18 Dec. 2018, www.usatoday.com/story/money/business/2018/12/18/craft-beer-expands-more-than-7-000-breweries-us/2206013002/.
2 Cholin, John M. “Woodworking Facilities and Processes.” Fire Protection Handbook. 20th Edition. Arthur E. Cote. Quincy: National Fire Protection Association, 2008. Page 9-13. Print.