FRUIT RIPENING AND THE FIRE CODE
FIRE PREVENTION BUREAU
People don’t like green bananas. They don’t like black, mushy bananas very much either. People want perfectly ripe bananas to eat.
Before bananas and other fruits arrive in the grocery store, they are processed to make them ripe for consumption. It is this fruit-ripening process that poses a potential fire hazard.
As bananas, tomatoes, avocados, honeydew melons, and other fruits ripen naturally, they generate ethylene gas, a flammable gas with a flammable range of 2.7 to 36 percent.
Food processors can artificially initiate the ripening process by exposing the fruits to ethylene gas. Essentially, ethylene gas is introduced into specially designed ’’tight’’ ripening rooms under controlled conditions. Typically, the rooms are maintained at about 60 F, with a relative humidity of 90 percent. The fruits usually are “gassed” for between 18 and 24 hours but remain in the tight room for a few days so they can “age” slowly and to avoid “runaway” ripening.
FORGOTTEN PROVISIONS
The model Uniform, Standard, and National fire prevention codes all have chapters dealing with fruit (crop) ripening. The National Fire Prevention Code also specifically covers the use of ethylene gas to “color” tobacco. National Fire Protection Association Standard 1, Fire Prevention Code, does not specifically address the fruit-ripening process. The fruitripening provisions in the fire codes appear to have become “forgotten” chapters. They tend to lag behind the current technology as it relates to ethylene gassing operations.
For many years, ethylene gas stored in cylinders has been “piped” into the ripening rooms. These cylinders are opened and gas flows through the pipes into the ripening room. Although the fire codes require that the ethylene be introduced under “positive control and measured” to avoid putting too much gas in the ripening room, explosions have occurred nevertheless.
(Photos by author.)
About 20 years ago, a new ethylene gassing technology was developed for ripening rooms. “Catalytic” ethylene generators were developed that actually produce ethylene gas within the ripening room itself. Unfortunately, the fire codes do not specifically address catalytic ethylene generators.
Catalytic generators use a liquid mixture of ethanol and methanol (plus some other materials) that is vaporized by a small heating element in the generator, eventually filling the room with ethylene gas. When full, the generators typically use about a quart of this liquid mixture, although slightly larger sizes are available. A quart of the liquid w ill produce about 10 cubic feet of ethylene gas.
Although ethylene cylinders are still being used, many facilities are converting to the use of ethylene generators. Economics, ease of use, and the desire to minimize the explosion hazard appear to be the driving forces behind the change.
FIRE CODE REQUIREMENTS
The fire codes require that the concentration of ethylene in a room not exceed one part ethylene per 1,000 parts of air (a 0.1 percent concentration), so as to avoid an explosion. Fire inspectors must analyze each ripening room with respect to room size and the quantity of ethylene gas that will he introduced into the room.
The fire inspector first must calculate the total volume of the room in cubic feet, subtracting the volume of the boxed fruit and other items in the room. The inspector then must compare this volume with the amount of gas to be introduced, to determine the anticipated concentration. If that figure exceeds 0.1 percent, then the quantity of ethylene introduced must be reduced.
The fire codes require that ethylene cylinders be constructed in accordance with nationally recognized good practice. Only cylinders actually being used may be located inside the building, although no more than two portable Department of Transportation/Interstate Commerce Commission containers may be stored inside when located in specially designed storage rooms. The system’s piping must be iron, and flexible connectors must be of an approved type. If tubing is used, it must be brass or copper, with a wall thickness of no less than 0.049 of an inch.
“No Smoking” signs must be posted at the entrance(s) to the ripening room. Obviously, smoking is not permitted in these rooms. The rooms also must be frequently cleared of combustible materials.
Artificial illumination in the room must be by electrical fixtures (see additional electrical requirements below). Heating must be by indirect means, such as by low-pressure steam; hot water or warm air; or approved electric, gas, or kerosene heaters. If combustion-type heaters are used, they must have sealed combustion chambers. Open-flame heaters and “open lights” must not be used in ripening rooms.
Steam and hot-water pipes and radiators must have a clearance of at least one inch to combustible materials. Gasand fuel-fired heaters must be installed in accordance with appropriate mechanical codes. Specifically, gas heaters must be equipped with an automatic pilot device to shut off the gas supply when the flame is extinguished. Combustion air for gas and kerosene heaters must be taken from the outside of the building. Products of combustion must be vented to the exterior.
If electric heaters are used, they must be of the types whose surface temperatures do not exceed 800°F. The thermostatic elements in these heaters must not produce sparks and must be approved for use in hazardous locations. Finally, guards stationed around heaters must prevent them from being hit by vehicles or lift trucks.
ELECTRICAL REQUIREMENTS
Ripening rooms must be studied carefully to determine if an explosive atmosphere exists or could exist. The electrical inspector must decide whether electrical equipment specifically listed for hazardous atmospheres is necessary.
The National Electrical Code stipulates that classified electrical equipment be used if an explosive atmosphere exists. If a potentially explosive atmosphere exists, such as through breakdown or faulty operation of equipment/processcs that might release ignitable concentrations of gas, classified electrical equipment must be utilized. In these hazardous cases, Class I, Division 1, Group C equipment must be used.
In ripening rooms that use catalytic generators, classified electrical equipment may not be necessary. Obviously, it is more difficult to accidentally “overgas” a large ripening room when using the generators (in some cases, the generators would have to be filled several times to create an explosive atmosphere).
A facility’s classification with regard to electrical requirements rests with the electrical inspector, with assistance from the fire inspector. Depending on the quantity of ethylene gas used, the building could be classified as a hazardous occupancy under the building code. As with all potentially hazardous occupancies, the fire inspector must conduct thorough research in order to render an appropriate fire code ruling *
