Addressing your second question, no, it may not be a big deal to create an H-occupancy storage room. The fire and building code requirements in this case (small storage room for distilled liquor) for H3-occupancy are not very high. If we assume that allowable areas is not an issue, the only requirements are ventilation of one cubic foot per minute per square foot of storage area, backup power, 1-hour rated walls and doors, and an automatic sprinkler system for steel barrel storage. Only 1-hour rated walls and an automatic sprinkler system are required for wood barrel storage. These requirements are summarized in Table 1.

Table 1. Distillery Storage Requirements

Let’s be more specific. For a small storage room, ventilation results in installing a wall mounted exhaust fan near the floor and vented to the outside**. While the fan will have to have backup power, due to its small size battery backup may suffice. The storage room will have to have 1-hour rated walls and doors and an automatic sprinkler system. Many rooms are already considered 1-hour rated, and therefore no changes are required (all wall penetrations have to be 1-hour rated). A 1-hour fire rated door may have to be added, or already exists. Upgrading automatic sprinkler systems for a small storage room may be as little as changing out a few sprinkler heads. Sprinkler design densities will depend on storage height, storage method, container type and size and ceiling height.

The advantages of having a separate storage room go far beyond the need for fire or hazard protection:

• Separated from other hazardous areas (production floor), this may minimize business down time and expense in the event of an incident.
• Processes can be better controlled in a separate room (including temperature and humidity).
• Distilled liquor is a high-value commodity and is easier protected in a separate room.

** Wooden barrels are exempt in the fire code, which means no ventilation is required. However, ventilation is strongly recommended for H-occupancies due to evaporation out of the barrels (“Angels’ Share”). It is up to the AHJ (Authority Having Jurisdiction) to determine applicable requirements. If ventilation is required and continuous ventilation in wood barrel storage is of concern based on excessive evaporation out of the barrels affecting flavor and reducing amounts, a Lower Flammable Limit sensor can be installed. The sensor causes the start of ventilation only when vapor fumes exceed 25% of their flammable limit. This can help minimize risks from vapors within the room (“Angels’ Share”). This proposed exhaust/ sensor approach is not in the codes and therefore may need to be approved by the AHJ.

Finely divided solid material which is 420 microns or less in diameter and which, when dispersed in air in the proper proportions, could be ignited by a flame, spark or other source of ignition. Combustible dust will pass through a U.S. No. 40 standard sieve.

There is a size limitation in this definition. The Fire Code will not classify anything greater than 420 microns as combustible dust. Additionally, after the dust is wetted, the dry ingredients are no longer considered combustible dust. However, with most dry ingredients some portion of the material will be small enough (similar to the bottom of a cereal box) to be considered less than 420 microns.

The current definition in NFPA 654 ² is “a combustible particulate solid that presents a fire or deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations, regardless of particle size or shape.” Again the reasoning here is that material can break down during shipping, conveying, mixing, and use. It will then become an immediate hazard in its dust form, if a source of ignition is available.

Therefore dry combustible dust does exist in (breweries and) distilleries, especially when these dry ingredients are being poured into tanks to make “mash”. Fire departments typically require dust collectors in areas where dry ingredients are being dispensed. Additionally housekeeping, which is more commonly maintained in a distillery than a standard industrial occupancy, is critical to keeping the dry dust on surfaces to a minimum.

Why is dry dust on surfaces critical since only suspended dust in air creates an explosion hazard? Major dust explosions typically occur as a secondary incident. Usually a smaller incident caused by air turbulence creates a disturbance of the dust particles, suspending them into air. Once suspended in air, a secondary incident occurs when the dust mixed with air reaches an ignition source resulting in an explosion.

An example of an investigation to evaluate the potential of a dust explosion hazard in a distillery is discussed in detail in the article “Assessing Combustible Dust – New Codes”. The straightforward calculations are based on the ‘layer depth criterion method’ prescribed in NFPA 654 and use floor dust layer thickness and area of the dust accumulations as inputs.

Before we attempt to address this question, let us provide some background on the commodity classification of the Fire Code to specify the necessary sprinkler protection scheme: Two sets of regulations typically apply to palletized or rack storage of flammable liquids; high piled storage regulations and hazardous materials regulations. Depending on whether the AHJ (Authority Having Jurisdiction) allows the storage to fall under the exemptions called out in the Fire Code ^4,5 (Section 5001.1 and Section 5701.2), the hazardous materials regulations, may not need to be applied.

If the exemptions are not deemed applicable, the more stringent requirements of both hazardous materials protection regulations and high piled storage regulations have to be applied. But if the storage is exempted out of the hazardous materials chapters of the Fire Code, how well do the protection schemes in the high piled storage chapter perform in the event of a fire? Can this storage truly be treated, and adequately protected, as a Class IV commodity?

Let’s look at two specific examples and compare the sprinkler requirements to the results of the FM fire tests: A sprinklered building and 100-proof distilled goods filled in glass bottles and packaged in cartons stored in the following configurations:

• 16.5-ft palletized storage with a 30-foot ceiling height
• 30-foot rack storage with a 35-foot ceiling height

Per NFPA 13 protecting storage in palletized or rack storage configurations requires the following ceiling densities when CMDA (Control Mode Density Area) sprinkler protection is applied:

• 0.22 (0.29) gpm/ft² over 2000 ft² for Class IV for palletized storage
     and high (ordinary) link temperature (NFPA 13 Figures 14.2.4.1,
     14.2.4.2 and 14.2.4.3)
• 0.3 (0.4) gpm/ft² over 2000 ft² for Class III for rack storage
     and ordinary (high) link temperature, in addition to in-racks
     (NFPA 13 Table 16.3.1.1)

For palletized storage these Class IV design densities, 0.22 (0.29) gpm/ft² over 2000 ft², are significantly lower than what FM Global successfully tested¹ in the latest series of fire testing (0.6 gpm/ft² operated 13 sprinklers while the fire propagated to the extent of the test storage array). This poses the question of whether palletized storage can be adequately protected despite the much lower design densities governed by Class IV protection requirements.

In the case of protecting the same goods in rack storage array, NFPA 13 prescribes sprinkler protection that are based on a classification of Class III, with in-rack sprinklers every 10 feet or 15 and 25 feet vertically, and a ceiling density of 0.3 (0.4) gpm/ft² over 2000 ft². This protection scheme is similar to what FM successfully tested (the in-rack sprinklers controlled the fire). Therefore protecting distilled goods in rack storage classified as Class III commodities to the configuration tested appears adequate. It is expected that applying the Fire Code’s mandated Class IV protection scheme, which requires in-rack sprinklers every 15 feet vertically and a ceiling density of 0.35 (0.45) gpm/ft² over 2000 ft², in addition to face sprinklers or horizontal barriers, will provide even better protection. However, how the protection compares for lower rack storage heights, where no in-rack sprinklers are required, remains unanswered.