`
`
`
`
`
`ESTA
`
`% E
`
`NTERTAINMENT SERVICES &
`TECHNOL 06 Y ASSOCI'A TION
`
`INTRODUCTION
`
`TO
`
`MODERN-
`ATMOSPHERIC
`
`EFFECTS
`
`2nd Edition
`
`Exhibit 1011
`
`
`
`Entertainment Services 66 Technology Association
`375 Sixth Avenue, Suite 2302
`
`New York.-NY10'001. [SA
`
`
`
`
`
`Exhibit 1011
`
`

`

`Basic
`
`Fog Use
`Guidelines
`
`v I Determine appropriate technology for application.
`
`0 Deliver only as much fog as necessary.
`
`' Deliver fog only where it is necessary.
`
`0 Deliver fog only when it is necessary.
`
`_
`
`U Avoid exposure of personnel to d1rect outflow of Fog
`generating devices.
`
`I Monitor and control condensation.
`I
`Post appropriate warnings.
`
`0
`
`I
`
`Follow manufacturers instructions.
`
`Read this booklet.
`
`PUBLISHED BY
`Entertainment Services 8: Technology Association
`875 Sixth Avenue, Suite 2302, New York, NY 10001, USA
`Phone:
`(212) 244'] 505
`Fax:
`(212) 2444502
`Email: standards@esta.org
`WW: http:ffww_esta_orgi
`
`_._‘.
`
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`
`
`ENTERTAINMENT SERWCES &
`Tscmomsr Assocmnom
`
`INTRODUCTION
`
`TO
`
`M ODERN
`
`ATM O SPHERI C
`EFFECTS
`
`2nd Edition
`
`This booklet is designed to inform you about current fog—making
`technologies and give suggestions for their safe and effective use.
`ESTA does not endorse any specific ng—making technology,
`product or technique.
`
`© 1996, 1998 Entertainment Services 81 Technology Association.
`All rights reserved. Second edtion printing: February 1998
`
`

`

`
`
`
`
`
`Table of
`Contents
`
`Introduction
`
`Introduction3
`
`Heated Fogs
`
`Cryogenic Fogs
`
`5
`
`10
`
`Mechanical Fogs .................................................... 14
`
`Working With Fog ................................................. 17
`
`Glossary ................................................................. 2 1
`
`Other Reading ....................................................... 22
`
`Acknowledgments .................................................. 23
`
`
`
`2
`
`Table ofContents ' ESTA
`
`The Greeks made stage smoke by burning pitch and resinous
`
`torches. Shakespearean audiences had to contend with sulfurous
`himes wafting across the stage as producers reached for atmospheric
`effects to enhance their theatrical events. This search for height-
`
`ened reality on stage has been an ongoing part of performances
`throughout the centuries. Today, productions commonly use gly-
`col and dry ice fog effects. The fog—making options are growing
`rapidly and now include crackers, water hazers, gas—propelled, and
`exotic liquid nitrogen technologies.
`Most early fog-making methods offered very little control over
`where the fog went. Today, nearly all equipment directs the fog to
`a specific location. Many fog machines are small and very portable,
`allowing fog to be generated and delivered to virtually any loca-
`tion. Remote control equipment allows the generation offog to be
`controlled from a location other than where the fog machine is
`
`placed.
`What are these technologies and how do they work? When is
`each appropriate and how can they be used effectively and safely?
`The use of stage armospherics is growing ever more routine. Yet,
`important information about the effects is scarce. Many producers
`and directors say, “I need smoke’“,” and send a technician to the
`local rental company to get a smoke machine. A technician plugs
`in the machine and presto, there is smoke.
`
`
`
`* Many people use smoke colloquially to mean either smoke
`or fog. However, smoke and fog are two very different things. Smoke
`is composed of solid particles suspended in the air and usually is
`produced by a burning or combustion process. Fog is composed of
`liquid droplets suspended in the air and can be produced by a vari-
`ety of processes, but not by burning. In preparing this booklet, we
`have very carefully used the words fog and smoke according to
`these definitions. In a few piaces, however, we defer to the collo—
`quial usage, so that the ideas will not seem foreign to you because
`of overly formal language. In those few places where we use smoke
`colloquially, the informal usage is signaled to you by putting the
`word smoke in this special bold-face type.
`
`ESTA ' Introduction
`
`3
`
`

`

`
`
`
`
`a5
`
`This “it’s magic" approach to atmospherics diminishes their
`
`benefits for everyone—producers, directors, performers, and tech—
`
`nicians. The information in this booklet is designed to help every—
`
`one work better with modern atmospheric effects, which are a gnaw—
`
`ing and valuable part of today’s entertainment technology.
`
`The fog that rolls in under the Golden Gate Bridge in San
`Francisco, or lies over marshy areas in the spring and fall, is com-
`
`posed of very small droplets of water suspended in the air. All arti—
`ficial fog systems create fogs that are small droplets ofsome liquid
`
`in the air. Glycol-based fog systems (the most common type of
`“fog machine") produce a fog in which the droplets are a mixture
`
`of water and glycol. Water—based systems, such as those using dry
`ice, liquid nitrogen, or high pressure water. produce a fog in which
`the droplets are water. Most cracker or gas-propelled fog systems
`
`generate a haze of a high—grade mineral oil or a glycol solution.
`This booklet describes each technology in simple terms. From
`
`each section, you will get a basic understanding of the technology,
`its effective use, as well as benefits and cautions. The OSHA and
`
`HSF. accepted safe concentrations of the chemicals used are in-
`
`cluded when they are available. Next, there is a brief discussion
`
`about how to work with a fog once you have put it in the air, and
`a table that summarizes the technologies. Near the end of the book—
`let, there is a brief glossary of terms. The technologies of modern
`
`atmospheric effects have grown beyond our current vocabulary to
`describe them. This glossary will help everyone speak the same lan—
`
`guage in the field of entertainment atmospherics. Finally, a brief
`
`list of additional reading material is provided.
`This booklet is not a substitute for the operator’s manual that
`
`fog machine manufacturers include with their products. If you do
`
`not m an operator‘s manual, get one. The manual includes im-
`
`portant details of the fog machine’s operation, which are beyond
`
`the scope of this booklet. Be sure you read the fog machine
`operator’s manual carefully and adhere to the manufacturer’s
`
`recommended operating procedures.
`
`This booklet covers all fog—making technologies, except those
`based on burning something, such as pyrotechnic methods. Burn—
`ing methods produce smoke, consisting of small solid particles,
`whereas fog consists of liquid droplets. The distinction is impor-
`tant.
`
`
`Heated Fogs
`
`V
`
`There are two heat—based methods for making fog—Hpump-pro-
`
`pelled glycol and gas—propelled fluid. Both methods propel a fluid
`
`into a heat exchanger and produce an opaque aerosol (fog). The
`
`glycol system propels a solution of one or more glycols (or some—
`times glycerin, a different but similar compound) and water with a
`mechanical pump or compressed air. The gas—propelled systems
`
`use a nonuflammable gas as the propellant for either high-grade
`
`mineral oil or a fluid composed of one or more glycols and water.
`
`Pump—propelled glycol fog systems were developed by Gunther
`Schaidt for opera companies in Germany, based on a new fog fluid
`
`concept. He introduced the idea to the United States in 1979. The
`innovation was such an improvement that it received an Academy
`
`Award in 1984. The system utilizes a series of glyc'ols of low mo-
`
`lecular weight diluted in deionized water.
`The glycol in glycol fog droplets helps keep them from evapo—
`rating and disappearing in the air. Glycol changes the refractive
`index of the vapor in a way that helps make the glycol fog visible.
`
`Highly efficient glycol fog machines can be designed to occupy a
`very small space, often no bigger than a bread box, and produce a
`long—lasting fog. These factors account for the high popularity of
`glycol fog systems in rental inventories and their very common
`usage.
`
`Gas-propelled fluid fog—making systems were also developed in
`the 19705. The fluid used is either a high—grade mineral oil or a
`
`solution of one or more glycols and water. The heated fluid prooess
`
`produces a very white fog composed of small droplets with a long
`hang-time. Because fluid usage decreases at a rate proportional to
`the cube of the particle diameter, the amount of fluid required is
`substantially less.
`
`How They “(dark
`V
`
`Pump—propelled glycol: A fog fluid containing a mixture of one or
`more glycols and water is moved from a reservoir (either a bottle or
`an on-board tank) into a heat exchanger by a pump. The heat ex—
`
`changer has been heated to the point at which the fluid will vapor-
`ize, usually less than 340°C (644°F). The fluid’s own expansion
`
`
`4
`
`Introduction ° ESTA
`
`ESTA ' Heated Fogs
`
`5
`
`

`

`
`
`
`
`into vapor forces the heated material out the front of the machine
`
`where. when it mixes with cooler air, it forms an opaque aerosol.
`
`The aerosol is composed of tiny droplets ofglycols that form around
`the dust that is naturally in the air. These droplets reflect the light,
`
`which is what gives this type of fog its characteristic white coloring.
`
`Gas-propelled fluid: The [l uid (high—grade mineral oil or a solu—
`tion of one or more glycols and water] that is stored in an on—board
`tank is mixed with a non—flammable gas, either carbon dioxide (CO;)
`
`or nitrogen (NJ). from a pressurized gas bottle. The mixture is pro—
`pelled into a heat exchanger. The heat exchanger is preheated to
`the boiling temperature of the fluid, which is different for mineral
`
`oil and each of the possible glycol solutions. The boiling fluid’s
`own expansion into vapor forces it out the front of the machine as
`
`an opaque aerosol. The result is a fog containing droplets with a
`diameter of between 0.5 and 4 microns. The size of the droplets
`depends on how much non-flammable gas was mixed with the fluid.
`In some cases, the pressurized gas also is used for purging purposes.
`Warning: Never use mineral oil in a pump—propelled
`glycol fog machine because this creates a fire hazard.
`
`All heated fog machines are capable of delivering anything from a
`wisp to billowing clouds of fog. This is accomplished by changing
`the pump flow rate or the flow rate of the pressurized non—flam—
`mable gas. This makes heated fog systems both versatile and dra-
`matic.
`
`A light use of fog lends a texture to the air. This allows the
`beams of light on stage to be seen, a very popular effect in this age
`of moving lights. A moderate use of fog allows for more dramatic
`effects like the battle scenes in Les Mummies, where there is an on—
`
`stage source for the fog. A heavy use of fog can cause a character to
`disappear in a cloud of smoke, such as the Wicked Witch in The
`
`Mm”! qfOz
`All heated fog machines convert fluid (glycollwater solution
`or mineral oil] to fog very efficiently. The machines are designed so
`that a light haze can be maintained for an entire performance with—
`out replenishing the fluid supply. When more fluid is needed, te—
`filling a machine is a quick, simple task.
`
`Efiettw Ute
`V
`
`6 Heated Fogs ' ESTA
`
`Several accessories expand the usefulness of these technolo-
`
`gies. If the fog is chilled after leaving the machine, the result is a
`
`low—lying fog effect simiiar to the traditional dry ice fog effect.
`Some manufacturers make chiller accessories that use cryogenic
`materials such as liquid carbon dioxide. See the section on cryo-
`
`genic fogs for information on how to use these cold materials safely
`and effectively. Most manufacturers now sell timers and remote
`
`controls for their equipment. Some fog machine manufacturers
`offer devices to allow their machines to be controlled by DMXS 12
`
`or analog lighting controlers.
`
`Pump-propelled glycol fog systems are economical, very popular,
`easy to obtain and easy to use. Both the production of fog and the
`
`volume of fog produced can be controlled remotely.
`
`Gas-propelled fluid fog machines can easily be left running dur—
`ing an entire production because of theit quietness and very low
`
`fluid consumption. Since the droplets produced by these machines
`
`are very small, they have a very long hang-time.
`
`Adjusting the volume of fog produced by a gas—propelled fluid
`
`fog machine is accomplished by opening or closing the regulator
`
`valve on the pressurized non-flammable gas bottle. Usually, the gas
`
`bottle is contained in the fog machine, but the gas bottle can be
`placed in a different location; In this case, appropriate hoses must
`be installed to transport the pressurized gas from the bottle to the
`fog machine.
`
`Consult the equipment manufacturer’s specifications and re—
`
`quirements to insure that the proper fluid is used in the equip-
`
`ment. Although manufacturers of fog systems and fluids may use
`
`some of the same components in their fluids, they do not necessar—
`
`ily have the same formulas. Likewise, each machine is designed to
`heat or vaporize the specific formula or formulas that the manufac—
`
`turer recommends. The minions-I)? between figflm'a’ composition
`
`and temperature settings and other intemalfiamm oftfaefi —meil7ing
`equipment is critical
`
`The relationship between machine and fluid is important since
`the under-heating of a specific fluid may lead to a wet fog that will
`
`ESTA ° Heated Fogs
`
`7
`
`Safety Gur’dir'nes
`V
`
`

`

`
`
`
`
`leave a residue and the over-heating of the fluid can lead to fluid
`
`decomposition. This decomposition or burning of the fog fluid
`may create harmful byproducts. In a recent report, the National
`
`Institute of Occupational Safety and Health (NIOSH) recom-
`
`mended, “using only fog fluids approved by the manufacturers of
`a:
`the machines.”
`
`Toxicity: While there are currently no accepted concentration stan-
`
`dards for heated fogs themselves, there are standards for some of
`
`the materials used in the fog fluids. W’hat are called glycol-based
`
`fluids generally use a combination of water, and one or more of the
`
`following chemicals: triethylene glycol, propylene glycol, diethyl-
`
`ene glycol, glycerin, dipropylene glycol, and butylene glycol. In
`
`the United Kingdom, propylene glycol has an Occupational Expow
`
`sure Standard (OES) of 470mg/m3 total, with a limit of 10mg! m3
`
`for the particulate component. Diethylene glycol has an exposure
`
`standard of 100mg/m", and for glycerin the standard is lOmgi'm".
`In the US, OSHA has set a Permissible Exposure Limit (PEL) for
`
`glycerin of 10mglm3. Highly refined mineral oil in both the UK
`
`and US has an exposure limit offimgfm3. All these limits are time-
`weighted averages over an eight—hour workday. Normal, healthy
`
`workers can be expected to work in atmospheres up to these limits
`without ill effects. MSDS information is available from most manu-
`
`facturers ofheated fog machines and fluids. Contact the man ufac—
`
`turer of your fog machine for the appropriate MSDS information.
`
`Do not modify or bypass the thermostat. Most fog machines are
`
`designed with thermostats that maintain the tight range of tern-
`
`peratures needed to achieve optimum fog production without over—
`
`or under—heating the fluid. In choosing a fog machine, make sure
`
`that it is equipped with a thermal cut-off device that will prevent
`
`“thermal runaway” of the machine causing safety and fire concerns.
`
`* Health Hazard Evaluation Report (HETA 90355—2449},
`United States National Institute for Occupational Safety and Health,
`
`1994, in text box on last page of the Summary (unnumbered).
`
`
`Never alter the contents of a fog fluid. For example, people fre—
`quently ask if it is possible to make the fog appear colored by add-
`
`ing pigment or dye to the glycol—based fog fluid. The answer is no.
`The heated adulterants may be unsafe to breathe. Also, adulterants
`
`could clog or damage the machine. Fog looks white because it re—
`
`fleets the light shining on it. If the light is white, the fog will reflect
`a white color. Should a colored filter be placed in front of the light,
`
`then the fog will reflect the same color. Thus, using colored light
`will achieve colored fog.
`I
`Similarly, perfumes or other scents must not be added to the
`
`fog fluid, unless recommended by the manufacturer. If you wish to
`have a scent present in conjunction with a fog effect, you should
`
`consult the manufacturer of your machine for their recommenda—
`tions.
`
`Do not use contaminated fluids. If your fluid contains foreign
`substances, the contaminates may clog or damage the machine,
`
`and may be propelled into the air. The heated contaminants may
`be unsafe to breathe.
`
`Beware of slippery residues. The use of fog machines can lead to
`
`a slow build up ofslippcry residue that is particularly noticeable on
`metal surfaces and sealed concrete floors. Care should be taken to
`
`insure that dangerous build-up does not occur on trusses, camalks,
`Stairways or anywhere else ivhere there is a slipping hazard. The
`residue may collect in air filters and clog them.
`
`Health Caution. Persons suflering from asthma or allergenic sen—
`
`sitivity may experience irritation, discomfort, or allergic symptoms
`
`when exposed to heated fog effects. Accordingly, manufacturers’
`
`literature should be consulted for specific health cautions before
`
`using equipment and fluids.
`
`Provide for quick emergency access to all fog machines. The
`small size of heated fog machines may tempt you to build one into
`
`a set. If you do so, be sure that the machine can be quickly accessed
`
`in an emergency. Remember, some components in die fog ma—
`
`chine get very hot and adequate ventilation must be provided to
`
`prevent overheating. Normal fire safety precautions musr be ob—
`served.
`
`8 Heated Fogs ' ESTA
`
`ESTA ° Heated Fogs
`
`9
`
`

`

`
`
`
`
`Cryogenic Fogs
`
`V
`
`Use a clean machine. Most heated fog machines require periodic
`
`cleaning. If such cleaning is recommended in your Owner’s Manual,
`then follow the manufacturer’s instrucrions.
`
`Dry ice is the oldest and most common of the cryogenic fog tech-
`
`nologies. It empioys very simple mechanical equipment that any—
`
`one can understand. Also, dry ice is relatively inexpensive and widely
`available.
`
`Liquid nitrogen was first used to create Fog eiFects in the 19703.
`
`The first use was in large rock and roll productions where pressur—
`ized liquid nitrogen was sprayed directly into the atmosphere cre-
`
`ating a micro weather system. The technique was called a “nitro—
`
`gen burst efiect.” Around 1985, Jim Doyle, a special effects techni—
`
`cian, refined the equipment and methods for creating Fog with liq-
`uid nitrogen and built the first commercial machines designed spe—
`
`cifically for the task. In 1992, he received an Academy Award for
`his pioneering work in designing liquid nitrogen fog machines.
`Cryogenically—created water fogs are virtually identical to naturally
`
`occurring fogs. Unless great care is taken, artificial fog disappears
`
`more quickly than natural fog, through either evaporation or con-
`
`densation. Often, a cryogenic fog tends to lie low to the ground.
`because of its low temperature. If yOu’ve ever flown over a fog-
`
`covered landscape. you know that this is really the natural course
`
`of things. It’s just that nature works on a much larger scale than
`most entertainment technicians.
`
`Cryogenic fog has the advantage of being odorless. Cryogenic
`fog systems put nothing in the air that is net already there in some
`
`quantity.
`
`How The}: “Kirk
`V
`
`All cryogenic fog egects are achieved by manipulating water to
`
`create droplets or by manipulating atmospheric temperature and
`
`humidity. The most common techniques for making this type of
`fog use a cryogenic material in combination with water to produce
`fine droplets in the air. Dry ice, which is carbOn dioxide Frozen
`
`solid at —80°C (—1 12°F) or liquid nitrogen at —198°C (—325°F}
`
`are the most common cryogenic materials. The cryogen is brought
`in contact with liquid water, a water spray, seine water vapor, or
`
`steam. The great temperature dillerence causes tiny water droplets
`to form and hang in the air. At the same time, the cryogen returns
`to its natural, gaseous state. The newly generated carbon dioxide
`or nitrogen gas requires a greater volume than its cryogenic precur-
`sor. In many cases, the increased gas pressure can be used to drive
`the fog through pipes and hoses to where it is needed, thus elimi-
`nating the need for fans.
`
`_
`
`Cryogenic burst eH‘ects manipulate the water already in the
`air. A cryogenic burst is created by spraying pressurized liquid ni-
`trogen or liquid carbon dioxide into the air. The cryogen experi—
`ences a rapid change in pressure and temperature that causes it to
`enter the gaseous state immediately. As the cryogen becomes a gas,
`it coois the water vapor in the surrounding air and forms a minia-
`ture cloud.
`
`Efictive Use
`V
`
`All cryogenically made fogs have a natural tendency to hug the
`ground, as a result of their low temperatures. Also, the carbon di—
`oxide (in log made with dry ice) is heavier than air and will move
`quickly to the lowest accessible space. Cryogenic fogs are well—suited
`to mysterious settings, but cannot be used to fill a space with mist
`to display light beams. Heating the fog, to make it rise, will simply
`make it evaporate. Blowing the fog upward with fans will have a
`similar result. Cryogenic burst effects, however, can achieve very
`impressive fog effects high in the air.
`
`Because liquid cryogens are extremely cold and stored under
`pressure, their use normally is limited to professional applications.
`
`54,939; GuMeJines
`V
`
`Handle cryogens carefully. The cryogens are extremely cold and
`should be handled with caution. Directly exposing your skin to
`cryogens can cause severe frost bite. Consult manufacturers‘ safety
`recommendations for proper handling procedures.
`
`Allow stored cryogens to vent. It is very difficult to keep cryogens
`at their extremely cold temperatures. As the solid and liquid cryo—
`gens warm, they become gases. You must allow this gas to vent. If
`you store a cryogen in a sealed container and prevent the gas from
`venting, the container will eventually rupture. Store dry ice in an
`
`10 Cryogenic Fogs . ESTA
`
`ESTA * Cryogenic Fogs 11
`
`

`

`
`
`
`
`ice chest with a loose seal. Store liquid nitrogen in a properly con—
`
`structed dewar or bulk storage tank.
`
`Beware of oxygen deprivation, especially in [Ow-lying places.
`
`Both carbon dioxide (dry ice) and nitrogen gases tend to dilute the
`
`oxygen in the air that the fog enters. Also, carbon dioxide in suff-
`
`cient concentration is toxic. Usually, these properties present no
`
`problems. However, considerable care is required if large volumes
`
`ofcryogenic fog are being used or cryogenic fog is being used in a
`confined area.
`
`If a performer or technician does not get enough oxygen in the
`
`air they breathe, they can become dizzy. If this happens, they must
`be revived quickly with fresh air. Also, these gases (especially car—
`bon dioxide, which is heavier than air) tend to accumulate in low-
`
`lying places. Never allow someone to lie down in a fog created by a
`
`cryogenic method. Be sure the orchestra pit, any other low—lying
`areas, and any cryogen storage areas have adequate ventilation.
`
`Look out for condensation, particularly with dry ice fog. It's
`hard to keep water vapor suspended in air. The water vapor may
`evaporate, in which case it just disappears. Or, the water vapor may
`
`condense, in which case you have puddles or a water slick all Over
`
`the stage, or any other flat surface that is in the way. Check your
`fog-making situation carefully to be sure that there is no condensa—
`tion (or at least no hazardous condensation). Check this before
`
`every performance. Slight changes in the air in the venue can pro-
`duce great changes in condensation rates. In addition to testing the
`fog syStem before performances, the stage manager should ask per-
`formers to report any condensation they detect while on stage.
`
`Maintain the fog-making equipment. Water, particuiarly mov-
`
`ing water, is abrasive and can cause significant wear on fog ma-
`
`chine components. This makes regular inspection of fog machines
`
`imperative to insure that all parts are in safe, efficient operating
`condition. Learn the maintenance schedule for your fog—making
`equipment and follow it.
`
`Hot water and dry ice can produce corrosive conditions inside
`
`the fog machine. You should change the water frequently in a dry
`ice fog-maker and check for signs of machine corrosion.
`
`Toxicity: Safe environmental concentrations for nitrogen and car—
`
`bon dioxide have been established by the Occupational Safety and
`Health Administration (OSHA) in the United States and the Health
`
`and Safety Commission (HSC) in the United Kingdom. The Health
`and Safety Executive in the UK also publishes guidelines for work—
`
`place safety, and there is legislation in the UK that applies to the
`atmospheres of specific work places.
`
`Nitrogen: Since nitrogen is not bio—active (that is it is inert insofar
`
`as your body is concerned), safe concentrations of nitrogen are stated
`in terms of remaining concentrations of atmospheric oxygen. The
`atmosphere is normally about 21% oxygen (0.»). Nitrogen can be
`added to the atmosphere until the oxygen level falls to 19.5%, ac-
`
`cording to OSHA regulations in the U.S., or to 18% according to
`HSE guidelines in the U.K. HSE also notes that the Mines and
`
`Quarries Act of 1954 requires that oxygen levels never be ailowed
`
`to fall below 19% by volume. Breathing air with reduced levels of
`
`oxygen causes impaired coordination and judgement, while lower
`
`levels of oxygen can lead to unconsciousness. Both automated and
`
`inexpensive hand-held 0: monitoring equipment are available.
`
`MSDS information is available from your industrial Gas Supplier
`
`or by Internet at http:.-"i’hazard.com.
`
`Carbon dioxide: Carbon dioxide is bio—active, aliecting respira-
`tion and the transfer of oxygen to the bloodstream through the
`
`lungs. The OSHA permissible exposure limit (PEL) time—weighted
`
`average for acceptable expomre over an 8—hour workday and the
`
`HSC Occupational exposure standard (OBS) for CO: is 5000 parts
`per million, or 0.5%. In the US. CO: also has a short term expo—
`
`sure limit (STEL) for no more than 15 minutes of 30,000 ppm
`(3%}, while the HSC short term limit is halfthat. CarbOn dioxide
`
`is weakly narcotic at 3%, causing reduced hearing acuity and in—
`creased pulse rate and blood pressure. Levels above 7% can cause
`unconsciousness in a few minutes. Both automated and hand—held
`
`CO: monitoring equipment are available. MSDS information is
`available from your industrial-gas supplier or by Internet at httpdi"
`hazardcom.
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`
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`12 Cryogenic Fogs ' ESTA
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`ESTA ' Cryogenic Fogs 13
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`

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`Mechanical
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`Fags
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`There are three mechanical methods for making fog: pressmized
`water, crackers, and ultrasonic. All these methods have the com—
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`mon theme that heating or cooling is not used and that some me—
`chanical process is used to manipulate a fluid to create the fog.
`
`Pressurized water Fog generation was originally developed by Tom
`Mee II (a cloud physicist) in 1969 to create a permanent cloud for
`the Pavilion of the Clouds at the Expo ’70 World’s Fair in Osaka,
`Japan. This technology has been enhanced since then into a com-
`mercial product with applications in many industries besides the
`entertainment industry. It is used in many situations where hu-
`midity, static electricity, and temperature must be controlled.
`
`Cracker Fog technology was developed in the 1960s as an improve-
`ment over previous fog-making techniques based on mineral oil.
`Previously, mineral oil haze had been generated by dropping the
`oil on a hot plate, which heated the oil to just below its flash point.
`The cracker method is considered to be a vast improvement, be—
`cause it uses no heat at all.
`
`In chemistry, crackingacompound means to decompose (break
`down or reduce) that compound using heat. In the petroleum in—
`dustry, cracking is the name given to specific parts of the oil relin—
`ing process. For theatrical fogs, cracker does not describe a chemi-
`cal process. These crackers work more like cracking a dinner plate;
`they break the fluid into small droplets.
`.
`The fluid used in crackers is usually high—grade mineral oil.
`The main advantages of mineral oil are its low vapor pressure and
`low rate of evaporation, which result in a fog with a long hang—
`time. Mineral oil also has the advantage that it produces an odor—
`less, pure white fog. There also are scucalled "water crackers” that
`use the same methodology, but crack a glycol-based fluid instead
`ofmineral oil.
`
`Cracker fog systems have become standard on many rock and
`roll tours. The haze that they create persists longer than most fogs
`under the atmospheric challenges of outdoor performances. The
`fine haze produced by crackers is perfect for highlighting laser light
`beams and the beams from conventional and moving lights.
`
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`14 Mechanical Fog ° ESTA
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`How The]; Wbrk
`V
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`Ultrasonic fog generation is the latest invention in fog technolo-
`gies. For several years. the use of ultrasonic transducers working at
`very high Frequencies (around 2 MHZ) to throw offtiny water drop-
`lets has been well-known as a technique for building humidifiers.
`Around 1994, this technique was adapted to work with a glycol
`and water mix, thus producing a persistent fog.
`
`Pressurized Water: Water at high pressure (typically over 1,000
`psi) is sprayed through a tiny nozzle so that it strikes the sharp end
`of a small rod. The water’s impact on the rod breaks the stream
`into tiny droplets. The droplet size, and hence the way the Fog
`floats in the air, can be controlled by varying the size of the nozzle
`opening and the water pressure.
`
`Crackers: A high—pressure air compressor is attached to a disper-
`sion systemwfor example, some brass fittings with tiny holes in
`the end— which is then placed in a vat 01': oil, usually high—grade
`mineral oil. When the air comes out of these holes and breaks the
`
`surface of the oil, tiny droplets of oil, 10 to 20 microns in diam—
`eter, are dispersed into the air. There are also so-called “water crack—
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`ers" that use the same technology, but utilize a glycol—based fluid
`instead of an oil.
`
`Fog crackers are nothing like petroleum industry crackers, the
`large towers you see at an oil refinery. Crude oil cracking is a pro-
`cess that reduces crude oil to chemically component products us-
`ing a combination of heat and catalysts. On the other hand, fog
`crackers break the fluid into small droplets, but do not change the
`oils chemical composition. Mineral oil cracker fog machines never
`use catalysts.
`
`Ultrasonic: An array of ultrasonic transducers is submerged just
`under the surface of a wealt (typically 10% to 20%) glycol and
`water mixture. The transducers break-up the fluid into tiny (1 to
`10 micron) droplets that drift in the air above the fluid. The drop—
`lets are then moved out oFthe machine by a Fan. The fog produced
`by this method comes out oFthe machine more as a fine haze than
`
`as a dense fog. The technique is relatively complex compared to
`
`others but has the advantage quuiet operation.
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`ESTA 0 Mechanical Fog 15
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`Eficflve we
`V
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`Fog generated by pressurized water can be made to rise well OFF the
`ground. Its greater loft has made it suitable For such diverse pur—
`poses as crop protection from frost and cooling patrons waiting in
`lines at summer theme parks.
`
`Crackers and ultrasonic fog machines normally are used to
`create a fine, almost invisible, haze to enhance light beams and add
`dramatic atmosphere. A high—grade mineral oil or low evaporation
`rate glycol is normally used in the fluid to give the haze a long
`hang—time. The machines are often lefi running continuously dur-
`ing a production, set to an appropriate output level to give a con—
`stant level of haze. They are particularly sensitive to drafis and air
`handling systems because of the relatively low output. A cracker or
`ultrasonic haze can be cooled to produce low-lying fog efFects.
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`o5
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`Safi’gi Gur'dlr'nes
`V
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`Pressurized water machines require maintenance. The water pres-
`surization hardware may require periodic maintenance; check your
`Owner’s Manual. The nozzle opening and the rod at which the
`pressurized water is directed will be eroded by the water and must
`be replaced. Water, particularly moving water is abrasive and can
`cause significant wear on log machine components. This makes
`regular inspection of fog machines imperative to insure that all
`parts are in safe, efficient operating condition. Learn the mainte—
`nance schedule For your fog—making equipment and follow it.
`
`Beware of slippery residues. The use of fog machines can lead to
`a slow build up ofslippery residue that is particularly noticeable on
`metal surfaces and sealed concrete floors. Care should be taken to
`
`insure that dangerous build up does not occur on trusses, catwalks,
`stairways or any