Important note: It is impossible to give a finite set of rules that will assure your safety in pyrotechnics. Described below you will find just some of the most important and common (‘everyday’) things that should always be kept in mind when handling pyrotechnic compositions and chemicals. They apply to a wide variety of compositions. But every composition is different. Some must be rammed or pressed to work properly. Other will explode when rammed. Some must be wet with water, others may spontaneously ignite when wet. Some mixtures are relatively safe to use by themselves but are extremely sensitive when used together (A number of well known ‘incompatible’ mixtures and chemicals are also listed below). The point is: remember and think about the rules below, they are important, but realize any such list is inevitably incomplete. Accidents happen even in places where every conceivable safety precaution is taken. We don’t guarantee your safety if you follow the rules below (also read the disclaimer below), but merely say it is wise to do so. It’ll increase your safety. 

Disclaimer
IBB.ch accepts no responsibility for persons harmed or injured or for any damage caused by devices like rockets, igniters, propellants etc. made on the basis of information presented on the IBB.ch web pages. Information presented herein is for informative purposes only. Also note that although we have tried to give comments on safety aspects of the described procedures, but we may have forgotten things or have been inconsistent. Keep that in mind at all times. Use your common sense, and use more than one reliable source of information before doing anything.

General Safety Precautions

With that said, a list of some generally useful safety precautions in no particular order:

  1. Never smoke when handling chemicals or compositions. Keep of children and pets or other people not involved in the process.
  2. Be sure you are familiar with all the properties of the compositions you work with. Thoroughly test new compositions for sensitivity, stability, compatibility with other mixtures etc., until you are absolutely sure that the mixture is ok to use in your application and method of construction. Find out as much as you can about other peoples experiences with a particular mixture.
  3. Chemicals that need to be finely powdered before use should be ground separately in a clean mortar with pestle or a clean ballmill or tumbler. Keep separate equipment for oxidizers and fuels. For cleaning equipment used for fuels, a solvent or sand may be useful. NEVER GRIND EXPLOSIVE COMPOUNDS OR MIXTURES!
  4. Do not mix large quantities of dry oxidizers (Ammonium nitrate, Ammonium perchlorate, potassium (per)chlorate, Potassium nitrate, Sodium nitrate etc) with fuels (hydrocarbons like sorbitol, starch, fine metal powders of Mg, Al, Ti, Zr etc). If possible use a compatible wetting agent like water (Do NOT use water with metal powders though!!), Ethanol, Acetone, Ether and so on and let the compound dry afterwards.
  5. Use only non-sparking tools. Make your tools from either: wood, paper, aluminum, lead or brass. Other metals and materials may spark (especially steel will).
  6. Paper bags or wooden containers are good to use for storing mixed compositions. Store compositions dry and cool. Avoid plastics (Electrostatic discharge) , glass and metal (Shrapnel’s) . Avoid storing compositions in general. Make as much as you will need in the near future and keep no more in stock than necessary.
  7. Never have large amounts of composition near you. If you must use larger amounts of composition in multiple items, store the bulk of composition in a safe place and bring only small amounts to your working place. Finished items should also be brought to a safe place immediately.
  8. Prevent contamination of chemicals and mixtures. Have separate tools for every type of mixture (i.e. blackpowder-like mixtures, chlorates, perchlorates, etc.) and clean them well with hot water and/or alcohol after use. It is no luxury either to have different sets of clothing for working with different mixtures. Wash them every time after use (dust collects in the clothing). If you have the possibility, have separate rooms or better yet: separate buildings for working with different types of mixtures/chemicals.
  9. Related to 8: Keep a clean working place. Fine dust easily spreads all over your working place. Keep chemicals in closed cabinets or in a separate building. Mixtures should not be kept in the working place anyway (see rules 6 and 7).
  10. Provide adequate ventilation. This is especially important when working with volatile solvents or (poisonous, flammable) powdered chemicals. Not only can you get yourself poisoned, vapor or dust may also ignite.
  11. Be aware of static electricity buildup. Electrically ground your working table, stand on a anti static mat which is grounded. Monitor humidity and keep it above 60% as a rule of thumb. This can be especially important in winter (on the Northern Hemisphere at least). Touch a grounded surface before you place things on it. Touch other people before handing over compositions or finished items. Wear cotton clothing (Or even better anti-static NOMEX clothing’s as sold by DuPont) , avoid synthetics (do not be tempted to wear fleece clothing if your working place is cold in winter). Work in a standing position, sitting on chairs increases the risk of static electricity and the chair is in the way when you need to escape. Simple things such as unscrewing a (plastic) bottle, unwinding some tape or even moving your arm may accumulate enough charge on your body to ignite a sensitive composition. The risk of static electricity is often underestimated or even completely ignored by beginning amateurs in pyro, while it is actually one of the major causes of accidents in both commercial/industrial and amateur pyro setups.
  12. Wear proper protective clothing. A face shield (Not just safety goggles), dust mask, heavy gloves and a leather apron are minimal. Wear cotton clothing or NOMEX. Hearing protection can be good but it also makes it harder to hear other people’s warnings.
  13. Provide safety screens between you and compositions, especially when pressing, ramming, sieving or in other ways causing frictions/shocks/pressure etc. If big quantities are involved have a remote controlled procedure (Video, robotics etc)
  14. Be prepared for the worst. Have a plan for when something should go wrong. Have a fire extinguisher and plenty of water ready (excepting for mixtures for which water would create a greater hazard than ignition like fine metal powders of Mg, Al, Ti, Zr etc). Think beforehand of what might happen and how you could minimize the damage. Know how to treat burns. Inform someone else so he/she can help in case of an accident. Have a fast escape route from your working place.
  15. Work location: The work location for compounding of low sensitivity propellant should be a minimum of 25 meters from any inhabited building, with distance to increase appropriately depending on the amount and type of material being used. All materials must be locked in proper storage facilities when not actually being used (Fuels and oxidizers separated). Finished propellant/motors will be stored in a proper magazine.
  16. Neatness: Keep the area where compounding is being carried out, clean and neat at all times. Oxidizers, powdered metals, and other ignition hazards will be treated with appropriate care to minimize the danger of accidental ignition, with special care taken to avoid “dusting” of fine material. Never have more than one open container of chemical within this area at any time.
  17. Chemicals: Become familiar with the associated literature, including MSDS’s for each chemical used. Don’t use “makeshift” chemicals, but instead will obtain technical grade or appropriate/equivalent purity for compounding. Learn about chemical incompatibilities (see below with some examples), avoid them (examples: ammonium compounds with chlorate compounds; aluminum and any nitrate). Never make substitutions simply to see “if this works”, but instead will engineer mixtures to meet the preselected criteria.
  18. Training: The initial phases of your work will be performed under supervision of a knowledgeable person, one who has been properly trained in that which you are doing. Your initial work will involve mixtures that have been well characterized by others and have found to be minimally sensitive. You will study regularly to learn more about the nature of your propellant and motor work. A good book about safety in pyrotechnics and rocket propellants is L. Edward Jones’ “Safety Manual for Experimental and Amateur Rocket Scientists”.
  19. Amounts: Work with small amounts of materials. For well characterized minimal hazard mixtures make no more than can be used within a reasonable length of time. Uncharacterized experimental mixtures will be made initially in quantity not to exceed one gram, until the mixture has been properly characterized as to sensitivity and other hazard.
  20. Legal: Work in compliance with federal, state, and local laws. The local authorities having jurisdiction will be aware of your activities. For people living in Switzerland look here.
  21. Testing: Test the (impact and friction) sensitivity of mixtures using the smallest practical amounts of the mixture. Carefully note and avoid any mixtures that are unduly sensitive. Test any motor design at least three times, by proper static test, before committing that motor to flight.
  22. Rocket Motors: Rocket motors will be constructed of materials properly selected and engineered. Don’t use makeshift materials. Each rocket motor will be designed so that its failure mode is longitudinal, and testing of such motors will be performed in a vertical mode until the propellant has been properly characterized. Yield strength of the casing material itself will be a minimum of 1.5 times the maximum expected stress.
  23. Waste: Dispose of scrap material and flammable waste from your operations properly, by remote ignition, on a daily basis or more often. Scrap and waste will not be allowed to accumulate.
  24. Carry out any other procedures needed to minimize properly the hazard to myself, to others, and to your surroundings.

Incompatibilities

Some combinations of chemicals lead to especially sensitive or unstable mixtures. There are many more of such incompatible chemicals/mixtures than listed here but these are some of the more commonly encountered types:

  1. Chlorates and sulfur. Mixtures containing both are not only very sensitive to friction and shock but are also known to ignite spontaneously. The sulfur reacts with water and air to form trace amounts of sulfuric acid. This will react with chlorates to form chlorine dioxide, a yellow explosive gas that will ignite most flammable materials upon contact. Addition of small amounts of barium or strontium carbonate to chlorate based compositions is sometimes done to prevent buildup of acid, even in compositions without sulfur. Many older texts on pyrotechnics describe the use of chlorate/sulfur based compositions. Today, many alternative and much safer compositions are available and there is therefore no excuse for the use of chlorate/sulfur mixtures. This also means chlorate based compositions cannot be used in items that also contain sulfur based mixtures. For example: chlorate based stars (Fireworks) cannot be primed with black powder. Nor can a urst charge be used with black powder primed stars (or stars containing sulfur).
  2. Chlorates and ammonium compounds. Mixing these will allow ammonium chlorate to form in a double decomposition reaction that takes place in solution (moisture speeds up the process). Ammonium chlorate is a highly unstable explosive compound. It decomposes over time producing chlorine dioxide gas (see chlorates and sulfur). Mixtures are likely to spontaneously ignite upon storage or may explode for no apparent reason. An exception seems to be the use of ammonium chloride and potassium chlorate in some smoke compositions. According to Shimizu this combination is safe due to the lower solubility of potassium chlorate (compared to ammonium perchlorate). I personally would still use these mixtures with great caution (or avoid them) since it seems inevitable that small amounts of ammonium chlorate will still form. The lower solubility of potassium chlorate will make it the -main- product in a double decomposition reaction but not the -only- product.
  3. Chlorates with metals and nitrates. These mixtures show the same problems as chlorate/ammonium compound mixtures. The reason is that nitrates can be reduced by most metals used in pyrotechnics to ammonium. The reaction rate of this reaction is increased by presence of water. Over time (for example when drying) these mixtures may spontaneously ignite or become extremely sensitive. The fact that ammonium forms in a relatively slow reaction is treacherous. These mixtures are referred to as ‘death mixes’ by some.
  4. Aluminum/Magnesium and nitrates. Mixtures of these compounds sometimes spontaneously ignite, especially when moist. The mechanism is assumed to be as follows: The aluminum reduces some of the nitrate to ammonium, simultaneously forming hydroxyl ions. The aluminum then reacts with the alkaline products in a very exothermic reaction leading to spontaneous heating up of the mixture. This can eventually lead to ignition. The reactions take place in solution and therefore moisture speeds up the reaction. The process is usually accompanied by the smell of ammonia. Some types of aluminum are more problematic than others. Stearin coated aluminum is generally safer to use. The whole process can be prevented in many cases by the addition of 1 to 2 percent of boric acid. This will neutralize the alkaline products. It is best to bind such compositions with non-aquaous binder/solvent systems such as red gum/ethanol. Since aluminum/nitrate mixtures are extensively used it is important to be aware of this problem which is why the combination is listed here.