CHEMICAL DATA NOTEBOOK SERIES #116: BUTYRALDEHYDE
BY FRANK L. FIRE
Butyraldehyde is a flammable, toxic, irritating, slightly corrosive, clear, colorless, volatile liquid with a pungent, sweet, and rancid odor. It is used in making drugs, dyes, paper, plastics, and rubber and as a raw material in the manufacture of many chemicals.
Butyraldehyde is the fourth compound in the analogous series of hydrocarbon derivatives known as aldehydes. The first three aldehydes are formaldehyde, acetaldehyde, and propionaldehyde. An aldehyde is a hydrocarbon derivative that has had a –CHO group substituted for a hydrogen atom on the molecule`s chain. Butyraldehyde is compared with these shorter-chain aldehydes below.
Flammability is butyraldehyde`s principal hazard. Its flash point of 20°F means that at any temperature equal to 20°F or higher, butyraldehyde generates vapors sufficient to form an ignitable mixture with the air near the point of release. Any release of butyraldehyde or its vapors presents a very dangerous explosion hazard if a suitable ignition source is available. In butyraldehyde`s case, any ignition source that produces a temperature of 446°F is “suitable.” This autoigniton temperature is so low that all common (and some uncommon) ignition sources are suitable for ignition. Butyraldehyde`s explosive range (from 2.5 to 10.6 percent) in air is not particularly wide, but its low flash point and very low autoigniton temperature more than make up for it.
The terms “flammable” and “combustible” liquids really are dangerous misnomers since liquids do not burn (liquids that have flash points below 100°F are termed “flammable”; combustible liquids have flash points at 100°F and higher). The terms can mislead firefighters and other emergency responders, who may be led to believe that when the vapors are ignited in air, they simply burn. Nothing could be further from the truth. What burns are the vapors released from those liquids as they evaporate. What inevitably happens at the ignition of the vapors of flammable or combustible liquids (or flammable gases, for that matter) is an explosion. And, if the ignition source is not near the source of the liquid`s release, the vapors of those liquids will accumulate and flow (vapors are fluids) downhill or along low spots in the terrain (if not disturbed by wind or other turbulence) until they find an ignition source. The resultant explosion then “flashes back” along the trail of vapors to the original source. Anyone caught in this path is in grave danger.
If the vapors are more or less contained in a particular area due to the terrain`s configuration or other factors, the resulting explosion could be devastating. The important thing to remember is that the first phenomenon that occurs on the ignition of any amount of vapors that burn is an explosion, not a fire. The fire will follow the explosion if there is anything left to burn.
Another dangerous property of butyraldehyde is its ability to polymerize. Polymerization is a specialized chemical reaction that allows a certain small molecule to react with itself to form a “giant” molecule called a polymer. This reaction is very exothermic (releases heat energy) and could be very violent, depending on the amount of butyraldehyde present, the material with which it is reacting, the type of container, and the speed of the reaction. Butyraldehyde will violently polymerize in the presence of heat, acids, alkalies, and peroxides.
Butyraldehyde will corrode mild steel, especially in the presence of moisture.
Inhaling butyraldehyde will cause coughing, irritation of the nose and throat, watering of the eyes, nausea, vomiting, and loss of consciousness due to central nervous system (CNS) depression. Prolonged depression of the CNS could cause death. Ingesting butyraldehyde will cause severe damage to the mucous membranes; ingestion of large quantities could cause death. If the liquid or high concentrations of vapors contact the eye, severe irritation and burns can occur. Repeated or prolonged contact of butyraldehyde with the skin can cause severe irritation by its defatting action (the solvent action of the aldehyde).
Butyraldehyde is considered a stable chemical, but it might react violently if it comes in contact with acids, alkalies, peroxides, strong oxidizing agents, and strong reducing agents. At high temperatures, a violent polymerization reaction may occur.
Since butyraldehyde is considered a very hazardous material, the community`s emergency response plan must be activated when there is any significant release. The environmental experts the plan will bring to the scene will be able to offer advice on how to avoid damaging the environment when employing the mitigation techniques the incident commander selects. Additionally, all the other resources activated by the plan can stand by in case the situation gets out of control. Firefighters will need the aid of all outside experts to safely handle a release of butyraldehyde.
At least in the beginning of the incident, treat releases of butyraldehyde as a release of any other flammable liquid. Approach from upwind and uphill. Eliminate all ignition sources, and restrict all nonessential personnel from entering the danger zone. All emergency personnel working the “hot” zone must be adequately protected.
Take all standard precautions to ensure that the liquid does not enter a sewer system or waterway. If possible, contain the release by damming or diking with soil or other material that can be pushed up around the spill to form a containment pond. A containment pit dug with available compatible material implements is better for containing a very volatile material such as butyraldehyde.
The major danger will be the explosive vapors being generated. The high vapor density of 2.5 means the vapors will flow along low spots in the terrain and stay together for a considerable distance. If these vapors find an ignition source, the resulting ignition will “flash” back to the source of the vapors, making a strong explosion possible.
To prevent the accumulation of explosive butyraldehyde vapors, apply water spray just downwind of the release. Of course, contain the runoff from this operation, since this water will contain a small concentration of butyraldehyde.
Another possible mitigation technique is to slow the production of vapors or prevent them from accumulating by covering the spill with alcohol-resistant firefighting foam. The foam may break down over time and may need to be replenished. The use of foam presupposes the ability to contain the additional volume of liquid created.
In addition to the explosion hazard caused by an accumulation of butyraldehyde vapors, a toxicity hazard will exist for anyone who wanders into such a location without proper respiratory protection.
The entry of butyraldehyde into a sewer system could cause the system to fill with explosive vapors. Immediately warn all sewage treatment facilities of the material`s entering the system. The concentration of vapors in the sewer probably will be above the upper explosive (flammable) limit, but the vapors are sure to be within the explosive (flammable) range at any opening (manholes or catch basins) in the system. An ignition source near such an opening could cause a citywide explosion. Keep all ignition sources from coming near such openings.
Butyraldehyde entering a waterway will float on the water`s surface and dissolve relatively slowly. Vapors will rapidly evolve. The danger to aquatic life depends on the size and type of waterway, the amount of product entering it, and the temperature and turbulence of the water. Alert downstream users of the water as soon as entry occurs. If the waterway is a river or stream with high banks, dangerous amounts of vapors may be flowing just above the water; explosive and toxic hazards would be very significant in this case.
Aeration techniques can be used to decontaminate water containing butyraldehyde if the water can be isolated or diverted. Certified, experienced experts should carry out this procedure. Firefighters should never be involved in the salvage or cleanup of any released material, whether hazardous or not, since they may be injured in the process. Also, the incident commander will be liable for any collateral damage done to the environment by his or her actions. The proper environmental authorities must decide if and when the water is safe for use.
Salvage of contained product is relatively safe and easy, but it still should be carried out by properly educated, trained, and equipped professionals. The shipper, seller, buyer of the product, or party responsible for the incident should do or arrange (and pay) for such work. In fact, all costs, including those of the fire department`s response, should be paid for by the party responsible for the incident.
If the released butyraldehyde is burning, alcohol foam, carbon dioxide, dry chemical, or water spray can be used to fight the fire. The actual fire extinguishing agent selected depends on the result of the incident commander`s size-up, the amount of material released, the form in which it is released, the amount of any particular extinguishing agent available, the terrain, the weather, the exposures, the number of personnel available, and many other factors. As in any fire involving a hazardous material, water used in mitigation techniques must be contained.
Water spray may be ineffective as a mitigation technique. However, applying water spray or fog directly to a pool or container of burning butyraldehyde will cool down the unburned product and may extinguish the fire. Since liquid butyraldehyde is lighter than water, any water applied to the release will sink beneath the water and cause the burning butyraldehyde to flow. Containing this extra volume must be considered.
As is the case when fighting any flammable liquid fire, all containers should be cooled by applying water by only the safest techniques. Your training will provide you with the techniques. All cooling water should be applied by unmanned appliances positioned as far away as possible.
Do not extinguish burning plumes from a leaking container until the release of vapors can be stopped. Even though butyraldehyde is a liquid, it is the vapors that are burning. Treat a leaking container of this material as you would a leaking gas container.
PROTECTIVE CLOTHING AND EQUIPMENT
Choose protective clothing and equipment that will prevent butyraldehyde liquid or vapor from contacting the eyes, skin, and respiratory system. Use splashproof chemical goggles and a face shield for eye protection and positive-pressure self-contained breathing apparatus (SCBA). Rubber boots, gloves, and aprons and other impervious clothing will offer protection. If total encapsulating suits are worn, manufacturers of such suits claim that material such as butyl rubber, natural rubber, neoprene, nitrile-butadiene rubber (NBBR), polyethylene, polyurethane (PUR), polyvinyl chloride (PVC), and styrene-butadiene rubber may offer protection. Another reference suggests that only butyl rubber and Teflon® will offer protection against butyraldehyde. This raises questions as to which materials offer what protection, and all hazardous materials response teams and other emergency responders must investigate this issue. To be totally safe, consult the manufacturers of the suits your department uses and the manufacturers of butyraldehyde about the degree of safety offered by each recommended material.
Inhalation. Move the victim to fresh air; keep him calm and warm. If breathing has stopped or becomes labored, administer artificial respiration (mouth-to-mouth resuscitation may expose the first-aid giver to the material in the victim`s mouth or vomit). Seek immediate medical attention.
Eye contact. Immediately flush the eyes with large amounts of water for 20 minutes, lifting the eyelids occasionally. Immediate medical attention is required.
Skin contact. Gently remove contaminated clothing, and wash the affected areas with large amounts of soap and water. If irritation continues after washing, medical attention is necessary.
Ingestion. If the victim is conscious, induce vomiting. Never try to force an unconscious person to vomit. Call for immediate medical attention while making sure the victim is warm and comfortable. n
IDENTIFICATION NUMBERS AND RATINGS
(Chemical Abstract Services)
(Standard Transportation Commodity Code)
(Registry of Toxic Effects of Chemical Substances)
(United Nations/North America)
(Chemical Hazard Response Information System)
(U.S. Department of Transportation)
Class 3, flammable liquid
NFPA 704 Rating
(National Fire Protection Association)
(International Maritime Organization)
3.3, flammable liquid
FRANK L. FIRE is the vice president of marketing for Americhem Inc. in Cuyahoga Falls, Ohio. He`s an instructor of hazardous-materials chemistry at the University of Akron as well as an adjunct instructor of haz mats at the National Fire Academy. Fire is the author of The Common Sense Approach to Hazardous Materials and an accompanying study guide, Combustibility of Plastics, and Chemical Data Notebook: A User`s Manual, published by Fire Engineering Books. He is an editorial advisory board member of Fire Engineering.