ecobites

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While fireworks may look great on the 4th of July, it is a good idea to avoid using them at home, since they are not friendly to the environment and they can also be unsafe.  If you want fireworks, go to a community display instead of doing them at home. However, each firework launched into the sky is a precisely formed assembly of chemicals and fuel, carefully calibrated to produce a particular effect – a red chrysanthemum spray accompanied by a powerful explosion, or a blue strobe, for example. Understanding how the contents of a firework produce the impressive variety of colors, forms, and sound intensities requires only a simple understanding of chemical reactions. Fireworks are used so frequently today in celebrations that it is easy to forget that they are dangerous explosives and not kind to mother earth.

Fireworks generate three very noticeable forms of energy: a tremendous release of sound, bright light, and heat. The tremendous booms heard at ground level are the result of the rapid release of energy into the air, causing the air to expand faster than the speed of sound. This produces a shock wave, a sonic boom.

The colors are produced by heating metal salts, such as calcium chloride or sodium nitrate, that emit characteristic colors. The atoms of each element absorb energy and release it as light of specific colors. The energy absorbed by an atom rearranges its electrons from their lowest-energy state, called the ground state, up to a higher-energy state, called an excited state. The excess energy of the excited state is emitted as light, as the electrons descend to lower-energy states, and ultimately, the ground state. The amount of energy emitted is characteristic of the element, and the amount of energy determines the color of the light emitted. For example, when sodium nitrate is heated, the electrons of the sodium atoms absorb heat energy and become excited. This high-energy excited state does not last for long, and the excited electrons of the sodium atom quickly release their energy, about 200 kJ/mol, which is the energy of yellow light.

The amount of energy released, which varies from element to element, is characterized by a particular wavelength of light. Higher energies correspond to shorter wavelength light, whose characteristic colors are located in the violet/blue region of the visible spectrum. Lower energies correspond to longer wavelength light, at the orange/red end of the spectrum.

Every year more than 8,000 people in the U.S. suffer injuries caused by the personal use of fireworks. Nearly half of the victims are children. A third of the injuries are caused by illegally obtained fireworks, and burns account for half the injuries. (An ordinary sparkler burns at a temperature of more than 1000°C!) The National Council on Fireworks Safety has valuable information on how to safely and responsibly handle consumer fireworks.

The National Fire Protection Association enforces stringent safety regulations for large fireworks displays. Spectators must be kept at least 840 feet from the launch area (that's based on the height and burst diameter of the largest shells). Shells may not be launched if winds are stronger than 20 miles per hour, because they could be blown off course. Nevertheless, many accidents occur with unregulated, informal neighborhood displays, when spectators attracted to the activities stand dangerously close to the launch area.

Fireworks manufacturers also go to great lengths to ensure safety, but even so, more than 20 workers were killed in firework plants in the U.S. between 1970 and 1995. Safety regulations require that buildings be separated by concrete blast walls and that roofs be weakened to ensure that any explosion travels upwards rather than outwards. In addition, most fireworks are still made by hand because metal machinery could produce sparks or static electricity which would ignite the explosives.

Many animals are frightened by the noise of fireworks and people are urged to leave their pets at home when they go to fireworks displays. Sadly, there are reports of dogs running away and some were lost.

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Environmentally Friendly Fireworks

Chemists continue to explore ways to make new pyrotechnic compounds and mixtures that are environmentally friendly. Two recent reports describe pyrotechnics made from high-nitrogen compounds that produce less smoke and particulate matter, and also replace perchlorates as oxidizers.

The most Eco friendly alternative to fireworks is to forgo explosions altogether; go to a parade, go fishing, grill out, camp out or help out. If you must see the sky festively illuminated, you might want to try a laser light show, which create dazzling displays of color without launching dangerous chemicals into the air. They may consume lots of energy, but so does the rampant production of single-use fireworks.

For more information on environmentally friendly fireworks see:

Chemical and Engineering News

For more on fireworks and illustrations of their construction, see:

the NOVA website