Smoke and Fog Hazards By Michael McCann, Ph.D., C.I.H. Introduction In the last 10 years, the use of fog and smoke to create atmosphere or special lighting effects has greatly expanded, due in great part to the influence of music videos. There are a wide variety of products and machines used to create smoke and fog effects, with varying degrees of hazard. This dadta sheete only discusses non-explosive materials that depend upon a change in physical state to create the effect, not a chemical reaction. Fog and smoke effects are created by generating a fine mist, a dispersion of very small particles, or an actual smoke by burning organic materials. All smokes and fogs are easily inhaled. Some chemicals used to generate the smoke or fog are toxic; however even chemicals that are not appreciably toxic can be irritating to the lungs. In particular, high risk groups such as people with asthma or other respiratory problems, children, or elderly, and people having to do deep breathing (e.g a musician playing a wind instrument or a singer) might be more susceptible to inhalation of any material. It is often difficult to obtain information on many of these products, even from Material Safety Data Sheets (MSDSs), because many manufacturers claim that the compositions are trade secrets. Manufacturers of these products often make extravagant claims as to safety. For example, many products state that the chemicals used have been approved by the Food and Drug Administration (FDA) for ingestion. However, the fact that it might be safe by ingestion does not mean it is necessarily safe by inhalation. Some manufacturers also claim that air sampling studies indicate that the concentration of their product in air is below the Occupational Safety and Health Administration's (OSHA) Permissible Exposure Limit (PEL). This is very misleading, since OSHA PELs and the Threshold Limit Values they are based upon are intended to apply to workers in industry and do not usually protect the general population, especially high risk groups as discussed above. Many manufacturers have done acute toxicity studies on their products. These animal studies only tell the effects of single exposures and not of repeated exposures. In addition these studies would not pick up reversible, respiratory irritation which can be crucial to actors or singers. Another problem is determining the length of exposure. The assumption is that these fogs are used only for short periods of time. However in film production, for example, a particular scene could be reshot many times, thus lengthening the period of exposure. Also in theater, actors could be exposed daily. In addition most theaters or motion picture productions do not have an efficient method for clearing out the fog between takes or scenes, so that there can be an accumulation of the fog chemicals over a period of time. This can result in longer exposures not only for the actors but also the crew. In attempts to evaluate the safety of some of these fogs and smokes, unions and other groups have had these products analyzed. In addition, the National Institute for Occupational Safety and Health (NIOSH) and others have conducted air sampling studies to try and evaluate the safety of the products. Hazards of Particular Fogs and Smokes Dry Ice Dry ice is one of the earliest types of materials used to create fog effects. Dry ice is frozen carbon dioxide, and when exposed to air it sublimes directly from a solid to a gas. The cold gas causes moisture to condense into a thick, low-lying fog. Dry ice is the safest way to generate fog except in enclosed spaces where the carbon dioxide can accumulate and reduce the oxygen concentration in the air. This could cause asphyxiation if the oxygen concentration falls below 19.5%. There would also be a hazard if someone was lying down in the dry ice fog. Petroleum Distillates Many of the earlier types of fogs were based on kerosene, fuel oil or other petroleum distillates. These were vaporized by heating to generate a fine mist. Unfortunately inhalation of these chemicals caused eye and respiratory irritation, chemical pneumonia, and narcosis (dizziness, headaches, nausea, etc.). In addition, the mist of these petroelum distillates is a fire hazard. I definitely recommend against any fog product containing fuel oil or other petroleum distillates. Zinc Chloride Smoke Generating Devices A number of companies sell smoke generators based on zinc chloride (e.g. smoke cookies, smoke pots, smoke candles, smoke bombs). Some of these also contain chlorinated hydrocarbons such as perchloroethylene, a suspect carcinogen. The smoke is generated by heating or burning the product, which is classified as a Flammable Solid, D.O.S. by the Department of Transportation. These are available in sizes that generate small to very large amounts of smoke. The Material Safety Data Sheets on many of these products are not adequate and do not reflect their hazards. Use of these smoke devices in fire fighter training exercises has resulted over the years in complaints of breathing problems, chest paints, hot and cold flashes, headache, fever, fatigue, sore throat, nausea, cough and even some fatalities. Some of these symptoms might be due to chlorinated hydrocarbons, but most are due to the generation of high concentrations of hydrochloric acid from the reaction of the zinc chloride with water. In some studies hydrochloric acid concnetration have been many times higher than OSHA PELs and even approach levels considered immmediately dangerous to life or health. Even lower levels of smoke has caused symptoms. I recommend against the use of zinc chloride smoke devices, or devices based on titanium chloride and similar materials indoors or in outdoor situations where either film crew or actors could be exposed to any substantial amount of the smoke. Ammonium Chloride Ammonium chloride (sal ammoniac) is a common method of generating smoke on stage and outdoors. The smoke is created by heating the ammonium chloride. Air sampling studies have found large concentrations of ammonium chloride, in some instances near the OSHA PEL for nuisance dusts. Air sampling studies have also shown that some decomposition of the ammonium chloride to hydrogen chloride occurs during this heating. The hydrogen chloride dissolves in water in the respiratory system to produce hydrochloric acid, a respiratory irritant. The levels of hydrochloric acid are much smaller than caused by the zinc chloride smoke devices, but are still high enough to cause concern. It is not recommended that ammonium chloride be used indoors or in enclosed spaces. Mineral Oil This includes oil crackers and diffusion foggers. Oil crackers involved bubbling air through a drum of mineral oil. The air bubbles reaching the surface contained "cracked" oil of particle size 1 to 50 microns. This oil is not "cracked" in the sense of chemically breaking down the oil but is merely creating smaller droplet size. This has also been used in combination with dry ice. The diffusion fogger produces a mineral mist of less than 1 micron size by using a compressor to force mineral oil through a series of fine filters. Air sampling studies by CalOSHA in an enclosed sound stage 90'x75'x30' found that ten minutes of fogging produced mineral oil concentrations for almost 2 hours that were 50% to 90% of the OSHA 8-hour PEL for mineral oil. However this PEL for mineral oil is based on its use as a cutting oil in industry; no toxicological studies have been made on inhalation of mineral oil of particle size less than one micron. However there is concern about long term problems such as lipid pneumonia since the very fine mineral oil mist gets deep into the lungs and stays there. This is not recommended for use indoors or where personnel could inhale the mineral oil. Glycol Fogs During the last decade, a whole range of products have been developed that use mixtures of water and polyfunctional alcohols, including ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol and glycerin. In general these are safer than most of the other fogs and smokes with the exception of dry ice. Ethylene glycol and diethylene glycol are toxic by ingestion, causing kidney damage and possible death; the other glycols mentioned are considered only slightly toxic. Ethylene glycol has been removed from most fogs after studies showed that it is a teratogen (can cause birth defects). Unfortunately long-term studies have not been done on inhalation of the mists of most of these glycols, although respiratory irritation is sometimes listed on Material Safety Data Sheets. A more serious concern is how the fog is generated. These mixtures are heated in a fog machine that heats the liquid to a temperature near 600 F. One air sampling study found significant levels of acrolein in the mist generated, about 20% of the OSHA PEL. Acrolein is a strong respiratory and eye irritant. NIOSH is conducting studies on various fogs to determine the extent of this decomposition product. It is likely that some chemicals could generate more decomposition products than others. Reformulation and finding ways to reduce the temperature needed to create the mist are possible solutions. Despite these problems, at this time the glycol fogs are probably the least hazardous fogs to use, although some will probably turn out to be safer than others. Burning Orgnic Materials The burning of gums such as olibanum gum (frankincense), paper, and other materials can also generate smoke. These smokes are irritating and considerable amounts of carbon monoxide may also be generated. In addition to the smoke hazards, there is the concern about the open flames. These materials should not be burned inside or where people would be exposed to substantial amounts of smoke. Types of Respirators The following table lists the types of respirators to use with different mists and fogs: Table 1. Respirator Selection for Smoke and Fog dry ice - none needed; test oxygen concentration in enclosed spaces. zinc chloride - acid gas cartridge and dusts and mist filter; high concentrations need air- supplied respirators ammonium chloride - acid gas cartridge and dusts and mists filter mineral oil - dusts and mists filter glycol fogs - organic vapor cartrdige and dusts and mists filter burning materials - dusts and mists filter for smoke. Recommendations 1. Smoke and fog on stage, television and motion picture sets is regulated by most Fire Departments. In New York City, for example, you need a fire permit to use smoke and fog just as you do for pyrotechnics. 2. All personnel (stage or camera crew, actors, etc.) should be informed in advance of the intention to use smoke or fog and the type to be used. Before use, there should be a discussion of the hazards and precautions being taken. 3. Obtain Material Safety Data Sheets on all smoke and fog products. In particular note whether the Reactivity section lists any hazardous decomposition products. 4. The choice of product depends on whether it will be used indoors or outdoors, in enclosed spaces, and whether people will be exposed for any significant period. 5. Children, elderly and people with respiratory problems should be informed of their possible higher risks. A medical opinion should be obtained as to whether they should be exposed. 6. Use only fog and smoke machines with the chemicals recommended by the manufacturer. Other materials may clog, or otherwise interfere with proper operation of the machine. Keep the fog machine in good repair and use as instructed. 7. Use the minimum concentration of smoke for the minimum period of time necessary. Avoid heavy concentrations when people are exposed. 8. Only allow essential personnel on the set or stage when using smoke and fog effects. Also evacuate any nearby areas where the smoke could reach. 9. On stages, interior sets or in enclosed areas, the crew should wear respirators. Respirators should also be available for anyone wanting one in any situation. All respirators should be NIOSH-approved. 10. On stages, interior sets or in enclosed areas, rapidly exhaust the smoke once not needed and between takes. Portable ventilators of the type used in manholes can be used (e.g. Coppus Engineering Corporation in Milbury, MA). In theaters it is particularly important to exhaust the fog away from the audience or orchestra pit. There have been situations where children in the audience have gotten ill because of exposure to fogs drifting from the stage. Outdoors, large fans can be used to blow away the smoke. 11. For motion picture production, minimize the number of takes to further reduce exposure of personnel. 12. When burning organic materials, have a fire watch on hand. Sources of Additional Help Written and telephone inquiries about hazards in the performing arts and entertainment industries will be answered by the Art Hazards Information Center of the Center for Safety in the Arts. The Information Center has a variety of written materials available on this subject. Permission to reprint this data sheet may be requested in writing from the Center. Enclose a self- addressed, stamped envelope for our publications list. Write: Center for Safety in the Arts, 5 Beekman Street, New York, N.Y. 10038. Telephone: 212/227-6220 This data sheet has been made possible through funding from the New York State Department of Labor, Occupational Safety and Health Training and Education Program. CSA is also supported with public funds from the National Endowment for the Arts, New York State Council on the Arts and the New York City Department of Cultural Affairs. (c) Copyright Center for Safety in the Arts 1991