STUDY MATERIAL FOR THE CERTIFICATE OF FITNESS EXAMINATION G-95 FOR G-38 TORCH USE OF FLAMMABLE GASES FOR CUTTING AND WELDING

Transcription

1 STUDY MATERIAL FOR THE CERTIFICATE OF FITNESS EXAMINATION G-95 FOR G-33 USE OF O 2 WITH FLAMMABLE GASES G-38 TORCH USE OF FLAMMABLE GASES FOR CUTTING AND WELDING G-39 TORCH USE OF FLAMMABLE GASES FOR JEWELRY TRADE 1998 New York City Fire Department All rights reserved

2 This study material contains the information you will need to prepare for the examination for the Certificate of Fitness for Torch Use of Flammable Gases (Cutting and Welding). The study material includes information taken from relevant sections of the Fire Prevention Code and the Building Code of New York. All questions on the Certificate of Fitness examination are multiple choice, with four alternative answers to each question. Only one answer is correct for each question. If you do not answer a question, or if you mark more than one alternative your answer will be scored as incorrect. A score of 70% correct is required on the examination in order to qualify for the Certificate of Fitness. Read each question carefully before marking your answer. There is no penalty for guessing. Sample questions 1. The oxygen cylinders used in an oxyacetylene system are made out of: (A) aluminum. (B) steel. (C) plastic. (D) copper. The correct answer is "B". You would mark "B" on your answer sheet. 2. When cutting or welding, the clothing that is worn should: (A) be sleeveless so the worker can stay cool. (B) have pockets to hold the acetylene key. (C) include flame resistant gloves and aprons. (D) be cleaned after work by blowing oxygen on the clothing. The correct answer is "C". You would mark "C" on your answer sheet. 2

3 OXYGEN AND FUEL GAS EQUIPMENT Oxygen and fuel gas equipment is commonly used in modern industry. This kind of equipment is used for heating, cutting, welding and brazing. It is used by welders, steel fabricators, builders, plumbers, jewelers, painters and many others. A mixture of oxygen and a fuel gas is used to generate a flame. The fuel gas is needed because oxygen does not burn by itself. Oxygen supports combustion. In other words, the oxygen intensifies the burning of the fuel gas. For this reason, workers should never use oxygen to blow dirt off their clothes. Even a small spark could immediately ignite the clothing and cause serious injury. Some of the fuel gases used for cutting and welding are butane, natural gas (methane), propane and acetylene. Acetylene is the most commonly used fuel gas. When acetylene is used with oxygen it is called an oxyacetylene system. Acetylene is used because compared to the other fuel gases it creates the greatest amount of heat when burned. The oxygen and acetylene are stored in separate cylinders. The oxygen and the acetylene are under pressure in the cylinders. Both cylinders have control valves on the top of the cylinder. The valves control the discharge of gas from the cylinders. Both cylinders also have protective caps. These caps prevent the valves from being damaged. The caps should be screwed on over the valve when the cylinders are not in use. The oxygen cylinder is made of steel and contains 100% oxygen. The oxygen is stored at pressures up to 2200 psi (pounds per square inch). The cylinder is painted green. It has a safety disk installed in the control valve connection. This disk will burst if the oxygen pressure in the cylinder becomes too great. This allows the oxygen to escape into the air and prevents an explosion. The pressure is likely to change if the cylinder becomes hot (for example in a fire). The acetylene cylinder is made of steel and painted black. It has a special honeycomb material inside the cylinder. The cylinder also contains acetone. The acetylene is dissolved in the acetone. The dissolved acetylene is stored at pressures up to 250 psi. This high pressure is needed to keep a sufficient amount of acetylene available for torch operations. The acetylene could not be stored at this pressure if the honeycomb material and the acetone were not present. Although acetylene is stored at higher pressures it is extremely dangerous to use acetylene at pressures above 15 psi. For this reason a regulator is installed on the acetylene cylinder. The regulator makes sure that the acetylene is discharged from the cylinder at no more than 15 psi. The acetylene cylinders have safety plugs installed on the top and bottom of the cylinder. These plugs melt if the cylinder becomes too hot for it to be used safely. The melted plugs allow the gas to escape slowly. This prevents the cylinder from exploding. The cylinders used for a portable oxyacetylene system are usually secured on a handtruck. The cylinders are less likely to be damaged when secured to a handtruck. The handtruck permits the cylinders to be moved safely. The portable system is usually used for on-site jobs. An example of a typical oxyacetylene welding system is shown on the following page. 3

4 A Typical Oxyacetylene Welding System A manifold oxyacetylene system is often used when work is always done at the same stations in the workshop. Several oxygen and acetylene cylinders are used to supply the torches in the workshop. The torches are connected to the cylinders using a series of hoses. The manifold system is also used to supply automatic cutting machines. The oxygen and the acetylene cylinders should be kept in an upright position when being used. This is true for both the portable and the manifold system. This is especially important for the acetylene cylinder. If the acetylene cylinder is used while on its side the acetone may escape. This may result in an explosion inside the cylinder. A control valve is on the top of each cylinder. This valve can be opened or closed to control the discharge of the contents of the cylinder. A handle is simply turned to open the oxygen control valve. A special key is needed to open the acetylene control valve. Before the cylinders can be used, a regulator must be attached to each of the control valves. The regulators are used for fine control of the oxyacetylene discharge pressure. The regulators are manually adjusted. The regulators are attached to the hoses. The hoses connect at the cutting, welding or heating torch. The two gases are mixed inside the torch. The torch operator controls the mixture of the gases by using valves on the torch. Adjusting the valves controls the shape and intensity of the flame. The oxyacetylene mixture is manually ignited by the operator when it leaves the torch. The flame itself can reach extremely high temperatures. A high temperature flame is needed to heat the metal. However, usually 4

5 it is not the flame that causes a fire. Instead, it is the thousands of sparks and pieces of hot metal that are generated when using the torch. The sparks and pieces of hot metal are all possible sources of ignition. In fact, sparks and pieces of hot metal are the source of ignition in about 60% of all fires in industrial occupancies. This number is greatly reduced when the operators are trained to use the equipment correctly. PROCEDURES USED TO PREVENT FIRES WHEN USING OXYACETYLENE EQUIPMENT Care must be taken to make sure that sparks and pieces of hot metal do not cause a fire. All torch operators and fire guards must hold a Certificate of Fitness. They must have this certificate in their possession during all torch operations. One fire guard is required for each torch operator. An additional fire guard is required one floor level below the work area. the fire guard makes sure that sparks do not cause a fire on the lower floor. The fire guards may use buckets of water or fire extinguishers to put out a fire. A cutting and welding station should be officially designated by the supervisor of the building. The supervisor works for the owner of the building. His job is to make sure that fire safety procedures are followed while welding or cutting in the building. This station should not be located near any combustible materials. All cutting and welding should be conducted at this station. When this is not possible the work must be supervised. An example of a welding and cutting station is shown below. A Welding and Cutting Station The supervisor cannot be the contractor hired to do the cutting or welding. The supervisor must be notified in writing when cutting or welding is to be done in the building. The supervisor must be notified at least 48 hours before the work is to be done. The supervisor should tell the contractor where the torch work can be 5

6 done safely. The supervisor should also give the contractor a copy of the safety regulations for the building. The contractor must follow the regulations. The supervisor must know and understand the safety guidelines outlined below. The supervisor should determine if there are any combustible materials in area surrounding the work area. No combustible materials should be located within 25 feet of the work area. Combustible materials are generally categorized as solid materials that burn. Paper, wood shavings, straw and fabric are examples of combustible materials. Some walls, portable partitions, ceilings and floors are also combustible. If possible, the combustible materials should be moved to a safe location. If they cannot be moved, they should be protected using fire resistant covers or curtains. They may also be wetted down as an added precaution. Any opening or ducts within 25 feet of the work area should also be covered. It is possible that sparks may enter these openings. This could result in fires in other parts of the building. The oxyacetylene equipment should only be used by trained and responsible personnel. Only the equipment approved by the Board of Standards and Appeals should be used. The work area should be well ventilated. This will prevent the worker from breathing dangerous fumes. Exhauster fans may be used to draw the fumes away from the work area. An example of a well ventilated work area is shown below. A Well Ventilated Work Area The workers should wear flame resistant gloves and aprons, skull caps, helmets or goggles, and safety shoes. Clothing with pockets or cuffs should not be worn while working. Sparks or pieces of hot metal might catch in the cuffs or pockets. The following picture shows the appropriate safety clothing to wear while cutting and welding. 6

7 Protective Clothing to be Worn While Cutting and Welding Under no circumstances should cutting or welding be done close to flammable or explosive materials. Flammable materials are generally categorized as either liquids or gases that burn. For example gasoline and propane are flammable materials. Trained fire guards should be present whenever cutting or welding is being done. The fire guards are not allowed to do any other kind of work while serving as fire guards. They must concentrate only on preventing fires. They should be on alert to make sure that the sparks do not start a fire. The fire guards should extinguish any fire immediately. They must have the appropriate fire extinguishing equipment available. For example, they may use garden hoses connected to a reliable water supply, fire extinguishers, or buckets of water. The entire work area should be checked twice for fires. The checks should be conducted one half hour and one hour after the torch work is finished. This is to make sure that there are no smoldering fires in the building. The fire guards must complete a signed inspection report. This report must be given to the supervisor of torch operations. The inspection report must be made available to any representative of the Fire Department. 7

8 SPECIAL PRECAUTIONS TO BE TAKEN WHEN USING OXYACETYLENE EQUIPMENT Containers that contain combustible materials should not be cut or welded. The container may catch fire and result in an explosion. Such explosions have caused serious injuries and several deaths. Even containers that have been empty for a while may be dangerous. They may still contain flammable vapors. All combustible and flammable solids, liquids, dusts, or vapors must be removed from the container before cutting or welding. The containers should be thoroughly cleaned with the correct cleaning solutions. Cutting and welding may cause sprinkler heads to accidentally open if the temperature rises near the sprinkler heads. When the head opens it sprays water on the surrounding area. To prevent this the head should be covered by wet rags. The rags should be removed immediately after the cutting and welding is finished. OPERATING INSTRUCTIONS FOR OXYACETYLENE CUTTING AND WELDING EQUIPMENT Do not allow any grease or oil to come into contact with the cylinder, fittings, regulators or hoses. The oil and grease are more likely to ignite in the presence of oxygen. This is because the oxygen intensifies the burning of other materials. The mixture of pressurized oxygen and oil or grease may also cause an explosion. Do not use the oxyacetylene welding or cutting equipment near any flammable materials. No flammable materials should be within 25 feet of the work area. When not in use the oxygen and acetylene cylinders should be stored in different enclosures. A sign should be posted outside each of these enclosures. The sign should be painted red on a white background. The sign should read: OXYGEN STORAGE NO SMOKING - NO OPEN FLAMES or ACETYLENE STORAGE NO SMOKING - NO OPEN FLAMES The oxygen cylinders are always green in color. The acetylene cylinders are always black in color. Under no conditions should the cylinders be used without the proper regulators installed. The oxygen cylinder should have a green regulator attached. The oxygen regulator and hose fittings have right hand threads. The acetylene cylinder should have a red regulator attached. The acetylene regulator and hose fittings have left hand threads. The regulators are not interchangeable. The hoses are also color coded. The acetylene hose is red. The oxygen hose is green. When using the oxygen cylinder open the valve fully. When using the acetylene cylinder open the valve one full turn only. The valve stem on the acetylene cylinder should always point away from the oxygen cylinder. The opening key must always be kept on the valve stem when the acetylene cylinder is in use. This allows the valve to be closed quickly in case of an emergency. When the cylinders are not in use the valves should be tightly closed. Before handling or transporting the cylinders make sure that the valves are tightly closed. 8

9 When using the oxyacetylene mixture the acetylene pressure should never be above 15 psi (pounds per square inch). If more acetylene is needed to supply the torch larger hose should be used. Never tamper with or attempt to repair the control valves on the oxygen or acetylene cylinders. Tampering with the valves is extremely dangerous. It may result in physical damage and serious personal injury. If the valves are damaged have the cylinder replaced by the supplier. The oxyacetylene cutting and welding equipment should only be used for purposes for which it was intended. It should not be used for any kind of tricks or stunts. This could result in serious or fatal injuries. Never attempt to mix oxygen and acetylene inside a cylinder. Never attempt to transfer oxygen or acetylene from one cylinder to another. Transferring acetylene from one container to another is extremely dangerous. The acetylene cylinder should not be placed near sparks or flames. For this reason, no cutting or welding should be done close to the acetylene cylinder. The cylinders should be located at a safe distance from the cutting or welding area. If a leak is noticed in the acetylene cylinder the cylinder should be taken out into the open air immediately. Care should be taken to make sure that the cylinder is not exposed to any open fires or flames. An explosion may occur if the escaping acetylene is ignited by an open flame. The manufacturer should be contacted and arrangements made for the removal of the cylinder. THE CORRECT WAY TO SET UP THE OXYACETYLENE CUTTING AND WELDING EQUIPMENT Before the oxygen and acetylene cylinders can be used several pieces of equipment must be attached. Only certified equipment should be used when using an oxyacetylene system. The valves on the oxygen and acetylene cylinders should be wiped clean first. The valves should then be opened for an instant. By opening the valve the pressure will blow out any dirt blocking the valve outlets. The oxygen control valve is opened by turning a handle. The acetylene control valve must be opened using a special key. The ends of the regulators should also be wiped clean. It is important to make sure that the valves and the regulators are clean. Any dirt in the valve outlet may prevent the oxygen or the acetylene from entering the hose. The regulators are then carefully attached to the appropriate cylinders. The green regulator attaches to the oxygen cylinder. The red regulator attaches to the acetylene cylinder. The regulator should be turned until it is hand tight. Then the regulators should be tightened using the a wrench. It is important to remember that the oxygen regulator has a right-hand thread and the acetylene regulator has a left-hand thread. The pressure adjusting screw on each regulator should be turned to the left (counter-clockwise) until it turns freely. A diagram of a typical regulator is shown on the following page. 9

10 A Typical Regulator The hoses should be attached to the appropriate regulator. The red hose is attached to the red regulator. The green hose is attached to the green regulator. The hose connections should be checked to be sure they are tight. The cutting, welding or heating torch should then be attached to the other end of the hose. The control valves are then opened. Always stand to the side of the cylinders when opening the control valves. The regulators are now adjusted to the desired pressure. The control valves on the torch should be opened when the regulators are adjusted. The acetylene pressure should never be above 15 psi. Examples of cutting and welding torches are shown on the following page.. 10

11 A Cutting Torch A Welding Torch When removing the equipment from the cylinders, first close the oxygen and acetylene valves. Then bleed any oxygen or acetylene in the hose line by opening the valves on the cutting or welding torch. Open the pressure adjusting screw on the regulator all the way. Then simply disconnect the regulators from the cylinders. Some operators prefer to disconnect the hoses from the regulators first. HOW TO DEAL WITH PROBLEMS THAT MAY OCCUR WITH THE CUTTING OR WELDING EQUIPMENT Backfire: This occurs when the flame on the torch goes out unexpectedly. A loud snap or pop may occur when the flame goes out. Sometimes the flame will quickly relight. This happens when the working surface area is hot enough to re-ignite the flame. Backfire may be caused by several things that are easy to fix. The following is a list of some conditions that might cause backfire. 11

12 (1) Touching the nozzle tip against the working surface. (2) Overheating the nozzle tip. (3) The oxygen and/or the acetylene is set at the wrong pressure. (4) The cutting or welding tip is loose or dirty. (5) Dirt on the work surface. (6) Kinks or blockages in the hoses. (7) The nozzle tip is damaged and not seated properly in the torch head. If backfire is noticed the cylinder valves should be closed and the equipment checked for the symptoms listed above. If any dirt or damage is noticed, it should be cleaned or repaired before the equipment is used again. Flashback: This occurs when the cutting or welding flame burns inside the torch or the hoses. It is usually accompanied by a whistling or hissing noise. As soon as the hissing or whistling is noticed the torch control valves should be closed. Then the acetylene cylinder valve should be closed. This allows the flame to burn itself out. After a few minutes the fire should have burned itself out. Flashback indicates that there is something seriously wrong with the equipment. The equipment should be checked for damage or blockage. Check for the same conditions that might cause backfire. A build up of dirt may also cause the flashback. This can be a very dangerous situation. Care should be taken to make sure that it is fixed properly. If the equipment is not cleaned and repaired correctly it may result in an explosion. The entire system should be cleaned and repaired if needed. If the flashback happens again, a qualified technician should repair the equipment. TESTING AND MAINTENANCE OF THE EQUIPMENT Regular inspection should be made to make sure that the equipment is functioning properly. All connections should be checked for leaks and physical damage. An oxygen leak cannot be easily detected because oxygen is odorless, tasteless and colorless. Acetylene is also colorless and tasteless. But an acetylene leak can be detected because of its strong pungent smell. When checking for leaks, a mixture of soap and water should be used. First make sure that all connections are tight. Then open the oxygen and acetylene cylinder valves. Each connection is then tested by brushing the soap and water mixture on the connection. Any air bubbles around the connections should be noted. If bubbles are noticed it indicates that there may be a problem with the connection. If bubbles are noticed tighten the connection and repeat the procedure. If the bubbles are still visible there is something wrong with the connection. The connection should be repaired or replaced before the equipment is used again. The hoses should be regularly checked for burns, cuts, worn places and similar defects. The hoses should be repaired or replaced when any serious defects are found. Sometimes the hose may be repaired by cutting out the affected area and splicing the hose. Taping is not an acceptable way to repair hoses. Copper tubing should never be used to splice the acetylene hose. The copper tube will react chemically with the acetylene. This reaction may cause an explosion if the tube is subjected to a physical blow. The regulators and the torch should also be visually inspected. If any part of the regulator or the torch is damaged it should be replaced or repaired. Repairs should only be made by a qualified technician. This is essential, since improper repairs to oxygen regulators have been responsible for a number of fires and serious personal injury. 12

13 STORAGE RULES Extra gas cylinders should be stored in areas that are protected from the weather. The protective caps should be installed. The cylinders should not be exposed to snow or direct sunlight. The cylinders should be raised on a small platform so the end of the cylinders are less likely to rust. The cylinders should be properly secured. The oxygen cylinders must be stored at least 25 feet away from any combustible materials. Suitable fire extinguishing equipment must be located near the cylinder storage areas. All cylinders should be marked "Empty" or "MT". This allows personnel to quickly determine if the cylinders are full or empty. USE OF OXYGEN-FUEL GAS SYSTEMS IN A MANHOLE Extreme caution must be taken when using an oxyacetylene system in a manhole or similar underground structure. When working underground there is a possibility of a build up of flammable liquids and gases in the structure. These liquids, gases and vapors sometimes leak from storage tanks, broken pipelines, or may have resulted from illegal dumping. Natural gas, fuel gas, refrigerant gas, sewage gas, and liquefied petroleum gas may leak into the manhole or underground structure. The flammable liquids found in manholes include various chemicals, and petroleum. These liquids and gases may be ignited by an open flame or sparks. When the gases or vapors are ignited it may cause an explosion. The explosion can cause serious injury or even death. Steps must be take to prevent explosions from occurring. When possible the entire manhole should be purged of the flammable gases and liquids. The work are should be ventilated. A strong fan should be used to force all gases away form the work area. The fan should be in operations at all times when working in the manhole. Water should be used to flush the manhole of flammable liquids. This flushing prevents the gases from being ignited by the open flame of the torch. After the manhole has been purged and while the fan is in operation the atmosphere of the manhole should be tested. The manhole is tested using a flammable gas indicator. This tool gives a reading of the amount of flammable gas in the manhole. The gas indicator does not measure the toxicity of the atmosphere. The toxicity can be measured using a gas analysis technique. This gas analysis must be conducted periodically. These tests must be conducted by a qualified individual. Adequate ventilation must also be provided in the work area. This prevents the worker from inhaling any toxic fumes that are in the manhole. Tests must also be conducted to determine the oxygen content of the manhole. Special equipment is used to assess the oxygen content. Under no circumstances should a worker be sent into a manhole if the oxygen content is below 19.5%. The only exception to this rule is when a worker is wearing a self contained breathing apparatus. The liquids and gases that build up in the manhole may be both toxic and flammable. They may also be suffocating. This is a health hazard. Therefore the worker must be adequately protected. USE OF TORCH FOR JEWELRY MANUFACTURING Heating torches are often used in jewelry manufacturing. The torch is used to heat metals as part of a soldering process. Solder is added to permanently bond the heated metals. Gold and silver solders are the solders most often used by jewelry makers. These solders are expensive and usually used when working with precious materials. The gold and silver solders offer a clean, strong and durable bond. Less expensive lead and tin soldering is sometimes used when dealing with less precious metals. For example, they may be used when soldering an item made of copper or when gilding metal. When the temperature of the torch flame is below 1000 Fahrenheit the process is called soft soldering. This kind of flame is used for small delicate soldering. For example, it may be used when soldering the setting 13

14 prongs onto a ring. When the temperature of the flame is above 1000 Fahrenheit the process is called hard soldering. This kind of flame is used to solder larger pieces of jewelry. For example, it may be used to solder decorative pieces to a heavy steel bracelet. A variety of torches and fuel gases may be used for soldering. The kind of torch used depends on the flame temperature and the control needed for the manufacturing process. The fuel gas is the gas that actually burns when discharged form the torch. Propane, acetylene, natural gas, and butane are all examples of flammable gases used in jewelry manufacturing. Oxygen or air are used in combination with these gases. Air and oxygen are not combustible. However, they are needed to support the combustion of the fuel gases. The torch operator controls the intensity and shape of the torch flame by adjusting the oxygen or air mixture supplying the torch. Acetylene Torch. Acetylene torches may be used in combination with compressed air or oxygen. The acetylene is stored in a specially designed cylinder under pressure. The oxygen is also stored in a cylinder under pressure. The acetylene and oxygen cylinders, regulators and hoses used in these systems are the same as those used for cutting and welding. When using the acetylene and air torch the air is automatically drawn into the torch chamber for combustion. The air is used to maintain and control a steady flame. When using the acetylene and oxygen torch the oxygen is forced into the combustion chamber. Both the acetylene and the oxygen are attached to the torch by a separate hoses. The oxygen is required to maintain and control the flame. Gas-Air Torch. These torches are supplied by a combination of a fuel gas and compressed air. Natural gas, and propane may be used as the fuel gas in this system. The compressed air is supplied by either an air compressor or a foot bellows. Propane Canister Torch. A small disposable container of pressurized propane gas may be used for soldering. The propane container is attached to a reusable torch. This arrangement is good for small jobs where limited heating is required. Mouth Blowpipe Torch. This system uses a torch attached to a fuel gas source by a hose. The fuel gas may be supplied by a propane or butane canister. It may also be supplied by a connection to the city gas supply. The connection to the city gas source is usually the most economical. The fuel gas feeds a small torch. The fuel gas is regulated by adjusting the fuel supply control. A metal tube is attached to the back of the torch. A hose runs from this tube to the operator's mouth. When the torch is ignited the operator supplies air to the torch by blowing through a mouthpiece. This allows him to control the intensity of the flame. With practice the operator can become very skilled in controlling the flame. An example of a mouth blowpipe is shown on the following page. 14

15 A Mouth Blowpipe Torch Bunsen Burner. This kind of system uses a simple mouth blowpipe and a Bunsen burner. The Bunsen burner is attached to a gas jet by a length of hose. For example, the burner may be attached to a gas jet on a kitchen stove. The Bunsen burner is used to control the gas. The gas is ignited as it leaves the Bunsen burner. A small steady flame is produced. This flame is then manipulated by a air blown from a blowpipe. The blowpipe is controlled by the torch operator. SAFETY GUIDELINES The supervisor of torch operations is the only person required to hold a Certificate of Fitness for torch operations in a jewelry manufacturing plant. He is responsible for the safety of all torch operators in the plant. He must make sure that they follow all safety rules that apply to cutting and welding. He must regularly check the pressure regulators, hoses and torch equipment. All equipment must be kept in good working order at all times. All defective or worn parts should be replaced immediately. Under no circumstances should a defective torch system be used. Use of a defective torch system may result in severe or fatal injury. Designated work stations must be assigned for torch use in the building. The torches should be used at these stations only. These stations must be located at least 25 feet away from any combustible and/or flammable materials. Soldering should never be done on a wooden surface. The top of the table or work surface should be made of a fire resistant material. 15

16 FIRE EXTINGUISHING DEVICES The Certificate of Fitness holder must be familiar with the different types of fire extinguishers in the building. He/she must know how to operate the extinguishers in a safe and efficient manner. He/she must know the difference between the various types of extinguishers and when they are may be used. What follows is a description of four classes of fire and the appropriate extinguisher to use on each. Class A fires are caused by ordinary combustible materials (such as wood, paper, and cloth), for which the quenching-cooling effect of quantities of water or solutions containing large percentages of water is most effective in reducing the temperature of the burning material below its ignition temperature. Class B fires are caused by flammable petroleum products or other flammable liquids, greases, etc., for which the blanketing-smothering effect of oxygen excluding media such as CO2, dry chemical or foam is most effective. Class C fires involve electrical equipment. The electrical non-conductivity of the extinguishing media is of first importance. These fire must be extinguished with non-conductive media such as CO2 or dry chemical. Class D fires are caused by ignitable metals, such as magnesium, titanium, and metallic sodium, or metal that are combustible under certain conditions, such as calcium, zinc, and aluminum. Generally, water should not be used to extinguish these fires. A Multi-purpose dry chemical fire extinguisher may be used to extinguish Class A, B, or C fires. Examples of several extinguishers are shown below. Symbols may also be painted on the extinguisher. They indicate what kind of fires the extinguishers may be used on. Examples of these symbols are shown on the following page. 16

17 The symbol with the shaded background and the slash indicate when the extinguisher must not be used. The Certificate of Fitness holder must understand these symbols. The Certificate of Fitness holder must make sure that the fire extinguishers are kept in good working order at all times. Usually, operating instructions are clearly painted on the side of the fire extinguisher. They clearly describe how to use the extinguisher in case of an emergency. An example of these instructions is shown below. Operation Instructions for a Fire Extinguishe r The certificate of fitness holder must know the locations of and how to operate all fire extinguishing devices that may be installed at the premises. He or she must also know the locations of any available fire alarm pull station on the premises and how to operate them. In case of a fire emergency, the certificate of fitness holder must activate the fire alarm, which will transmit an alarm to the Fire Department via a central station company. The certificate of fitness holder must know the telephone numbers of the local firehouse and the Fire Department Borough Communication Office should be known. The telephone numbers must be posted near the phones most likely to be used in case of an emergency. The borough communication office phone numbers are listed below. Manhattan (212) Bronx (718) Brooklyn (718) Queens (718) Staten Island (718)

18 FIRE EXTINGUISHER INSPECTIONS All fire extinguishers must be clearly visible. Signs must be posted indicating the locations of the extinguishers. Signs describing how to use the fire extinguishing devices must also be posted. The certificate of fitness holder must make sure that the extinguishers are inspected every six months. The fire extinguishers must be recharged after each time they are used or when required according to the type of extinguisher. The extinguishers must be inspected by a qualified technician at least once every six months. Generally, the inspections are conducted by a representative of the company who holds the maintenance contract for the extinguishers. The certificate of fitness holder should record the testing date and the technician's name in the inspection log. All inspections must also be recorded on a tag attached to the extinguisher. 18