Hazardous Materials and Safety Practices |
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AUTHORS’ NOTE
Although every effort has been made to ensure that the regulations and standard practices referred to in this text are current, recommended safety practices and associated regulations are always subject to change. Since the distribution of this book is not controlled, revisions to all existing copies is impossible. As a result, the technical information, such as material safety data sheets, is included only for educational purposes and should not be used in application. In addition, there are applications that are unique in one aspect or another. In these cases the recommended practices may differ from those used as general industry standard. Before attempting any activity, the aviation maintenance technician should review the most recent regulations, recommended practices prescribed by their employer, the associated equipment manufacturer’s recommendations, and the information provided by the manufacturers of any supplies being used.
INTRODUCTION
There are many specialized careers available to today’s aviation maintenance technician. As with any technical career, each career path has associated with it activities that can subject the technician and others to varying degrees of harm if performed without care. This chapter is intended to help the aviation maintenance technician identify potentially hazardous materials and ways in which the potential for harm can be minimized.
Today there are tens of thousands of products used in industry, with more being developed each day. Numerous governmental agencies (and, therefore, hundreds of governmental regulations) control the development, safety requirements, and health and environmental issues related to these products. Key among these agencies are the Consumer Product Safety Commission (CPSC), the Food and Drug Administration (FDA), the Department of Transportation (DOT), the Environmental Protection Agency (EPA), and the Occupational Safety and Health Administration (OSHA). Although all these agencies have some effects that may be felt in the aviation industry, the primary impact results from the last three organizations mentioned.
Some Federal Air Regulations (FARs) refer to the DOT standards in their text and use these standards as the criteria with which the aviation industry must comply. In addition, as users of potentially dangerous chemicals, the aviation industry must comply with both the regulations of the EPA as they relate to environmental concerns and OSHA as their usage relates to the safety and health of its employees.
Since the aviation industry is by its nature predominantly interstate commerce, most businesses in the aviation industry are subject to federal regulations. In addition, most state and some local governments have also passed safety and environmental related legislation that parallels or supplements federal legislation. As a result, the regulations associated with each are quite similar. Regardless of which jurisdiction applies to the operations of the aviation business, the operation must comply with some type of hazardous-materials regulation. In some instances, more than one jurisdiction may control the operations of the business.
Because of the vastness of this subject area and the general duplication of regulations between federal, state, and local governments, discussions in this chapter are limited to federal regulations and generic handling of hazardous materials. In addition to the information found in this chapter, in later chapters the aviation maintenance technician will find more safety data related to the specific types of equipment and/or processes as they are discussed throughout the text.
HAZARDOUS MATERIALS
The aviation maintenance technician frequently must work in potentially dangerous environments. In many cases, particularly when dealing with hazardous materials, the technician may not easily recognize those hazards. Some of these dangerous environments may be caused directly by the materials with which the aviation maintenance technician must work. In addition, exposures may be caused by other activities occurring in the area that are not directly related to the technician’s activities.
Hazardous materials are typically grouped into three categories: chemical agents, and physical and biological hazards.
Chemical Agents
Within the chemical agents category, four classes exist. Comprehensive Loss Management, Inc., a professional developer of and consultant for safety and health awareness systems headquartered in Minneapolis, Minnesota, has trade-marked the acronym FACTOR™ to help remember the classes of chemical agents. Much of the information in this chapter comes from and is included in their programs. Because each class of chemical agent requires different usage, handling, and storage techniques, it is important that the aviation maintenance technician be able to recall and identify each of these classes. FACTOR™ stands for
Flammable
And
Corrosive
Toxic
Or
Reactive
The two outside letters of the acronym FACTOR, F and R (flammable and reactive), become hazardous primarily after some outside event, condition, or substance interacts with them. For example, the necessary components for a fire to occur are fuel, oxygen, and heat. In that relationship, flammables are the fuel, and heat and oxygen are the outside agents. Reactives, when combined with certain other materials, are capable of generating heat and/or gases, causing an explosion.
The inside letters of the acronym, C and T (corrosives and toxins), on the other hand, act directly on the human body when exposure occurs. Exposing the skin, eyes, and other mucous membranes (such as the nose) to these elements can cause varying degrees of harm. Toxic agents cause poisoning. Aviation maintenance technicians should be particularly concerned when using toxic agents, because the ultimate effects of toxic poisoning are frequently delayed. It may take weeks, months, or even years for the poisoning to become apparent; because the toxic poisons are capable of using the bloodstream to move through the body, the cause-and-effect relationship may not be easily recognized.
As a general rule, when working with flammable and reactive agents, to avoid hazardous situations the aviation maintenance technician first needs to be concerned with exposing the agents to outside materials and conditions. Personal exposure to corrosive and toxic agents is the primary concern when dealing with toxins and corrosives. Therefore, the personal safety equipment used with corrosive and toxic agents should be designed to limit contact and/or exposure. Personal safety equipment designed for use with flammable and reactive materials is designed to limit heat exposure or impact, such as flying objects in the case of an explosion. In all cases, the recommended safety equipment recommended by the agent manufacturer, the employer, or the instructor should always be used.
Table 1-1 is a partial listing of frequently used chemical agents found in the aerospace industry. The aviation maintenance technician should be aware of the labels on the materials found in the work area and read them carefully.
Flammables (and Combustibles)
Flammables are materials that may easily ignite in the presence of a catalyst such as heat, sparks, or flame. They may be in any of the three physical forms: solid, liquid, or gas. Combustible liquids are very similar to flammable liquids, but they are not as easy to ignite.
Frequently found flammable or combustible materials in the aviation industry include fuels, paint-related products, alcohols, acetone, toluene, and some metal filings.
Generally Recommended Personal Safety Equipment
• Fire-retardant clothing
• Fire extinguisher
Handling and Storage
• Limit access to open flames, sparks, hot surfaces, etc. Note: Static electricity may produce sparks. To avoid sparks, containers should be grounded.
• Limit quantities to the minimum needed to accomplish the desired task.
• Store the materials in approved containers only and in designated areas only.
• Store flammable toxins and corrosive toxic materials separately. The corrosive gases could attack the flammable containers, eventually leading to a leak of flammable materials.
Typical Emergency Procedures
• Turn off electrical equipment or any other potential source of sparks.
• Attempt to close shutoff valve(s).
• Remove container(s) from the area.
• For large spills, leave the area immediately and notify your supervisor.
• In case of direct contact with skin or eyes, rinse immediately with water.
• If toxic substances are inhaled, go to a fresh-air area.
• If contact is made through clothing, remove wet clothing and store it in a proper container.
• Do not attempt to remove the substance with compressed air.
Corrosives
Corrosive materials are materials that can react with metallic surfaces and/or cause burning of the skin.
Frequently found corrosives in the aviation industry include acids and bases, such as battery acids and metal-cleaning solutions. Strong acids are most normally found in a liquid form, whereas bases tend to come in powdered form.
Generally Recommended Personal Safety Equipment
• Gloves, aprons, respirator, face shield or goggles, and, sometimes, protective footwear.
Handling and Storage
• Containers must be corrosive resistant.
• Eye (goggles and/or face shields) and skin protection (such as gloves) should always be worn.
• Never add water to acid.
• Acids and bases should be stored separately.
• Eye washes and showers should be easily accessible to the work area.
• Flammable toxins and corrosive toxic materials should be stored separately. The corrosive gases could attack the flammable containers, eventually leading to a leak of flammable materials.
Typical Emergency Procedures
• Remove any corrosives that have come in contact with your skin or eyes by rinsing with fresh water (approximately 15 minutes).
• Remove any contaminated clothing.
• Go to fresh air area.
• Ventilate area.
• Check safety equipment before attempting to stop the flow of spillage by creating a dam.
• If swallowed, DO NOT INDUCE VOMITING. Drink large amounts of water. Seek medical attention immediately.
Toxins
Toxins are generally defined as any substance that can cause an illness or injury. The effects of toxins, unlike flammables and corrosives, may appear all at once (called acute effects) or may build up over time with additional exposure (chronic effects). Some toxins may dissipate over time when further exposure is eliminated, while others remain in a human’s system, even after death.
Frequently found toxins in the aviation industry may be grouped into eight categories.
1. Solvents and thinners for bluing (such as Dykem), paints, ketones, and adhesives.
2. Solids such as metal dust or asbestos. Compressed air should never be used to clean metal dust from equipment or clothing. The use of compressed air may result in minute particles of material being embedded in the pores of the skin.
3. Machine lubricants, cutting fluids, and oils.
4. Gases such as carbon dioxide or nitrogen. These gases may not only possess a toxic nature but also displace the oxygen normally found in the air.
5. Polymers, epoxies, and plastics. Although not normally toxic in their final form, these materials possess toxic properties during the fabrication process.
6. Sensitizers, such as epoxy systems. Such materials react with and may destroy portions of the body’s immune system. The effects of sensitizers may be cumulative, so minimal levels of exposure are recommended.
7. Carcinogens. Carcinogens may cause changes in the genetic makeup of a human cell, resulting in cancer. Although the use of carcinogens is rare in the aviation industry, aviation maintenance technicians associated with cargo aircraft should pay particular attention to the cargo manifest before cleaning spillage.
8. Reproductive hazards, such as carcinogens. These hazards are rare in the aviation industry. Such materials may either interfere with the reproductive process (as in the cases of DBCP) or affect the developing process of the fetus (such as dimethyl acetamide).
Generally Recommended Personal Safety Equipment
• Gloves, aprons, respirator, face shield or goggles, and, sometimes, protective footwear are recommended.
• Be sure to use the environmental control systems that may already be in place, such as ventilation fans and filters.
Handling and Storage
• Minimize the release of toxic agents into the environment by capping all containers and storing them in properly ventilated areas. When toxins are used in open containers, such as dip tanks and trays, their surface areas should be kept to a minimum in order to reduce the rate of evaporation into the surrounding environment.
• Flammable toxins and corrosive toxic materials should be stored separately. The corrosive gases could attack the flammable containers, eventually leading to a leak of flammable materials.
Typical Emergency Procedures
• If there is any doubt in your mind regarding the degree of toxicity of the substance spilled, LEAVE THE AREA IMMEDIATELY AND NOTIFY YOUR SUPERVISOR.
• Generally speaking, if the spillage is less than 1 gal, it may be cleaned up by wiping it up with absorbent materials.
Reactives
Reactive agents are those materials that react violently with other materials (not necessarily solids). The reactions that may take place range from violent explosions to the emission of heat and/or gases.
The following reactives are frequently found in the aviation industry:
1. Oxidizers, which add oxygen to situations where high levels of heat and burning are present
a. Peroxides
b. Perchloric acid and chromic acid
c. Halogens, such as bromine and iodine
2. Water-reactive materials, such as lithium, react with water and form hydrogen gases, which are very explosive.
Examples of incompatible reactive materials include
• Cyanides (frequently used in plating) and acids
• Chloride bleach and ammonia (this combination forms highly toxic chlorine gas)
Generally Recommended Personal Safety Equipment
• Gloves, aprons, respirator, and face shield or goggles are suggested.
• Be sure to use the environmental-control systems.
Handling and Storage
• Store reactive materials in a location separate from other materials. Always review the MSDS (material safety data sheet) for incompatible materials.
• Many reactives are both toxic and corrosive.
Typical Emergency Procedures
• Shut down electrical equipment whenever possible.
• If there is any doubt in your mind regarding the degree of reactivity and toxicity of the substances involved, LEAVE THE AREA IMMEDIATELY AND NOTIFY YOUR SUPERVISOR.
Material Compatibility with Chemical Agents
Before leaving the topic of chemical agents, it is important to realize that although some materials meet the minimum standards for protective equipment in particular applications, other materials surpass these requirements. Table 1-2 lists various types of protective equipment materials and their relative effectiveness when used with common chemical agents. Although Table 1-2 provides generally accepted data, the aviation maintenance technician should always consult the MSDS, discussed later in this chapter, for specific protective equipment requirements.
Physical Hazards
Physical hazards are those to which the aviation maintenance technician is exposed that are usually caused by the use of some type of equipment not directly controllable by the technician. Typically, this type of hazard is generated by the operation of equipment that can be detected by the human senses. However, many physical hazards that fall into this classification are not detectable by the human senses. These hazards include X rays, microwaves, beta or gamma rays, invisible laser beams, and high-frequency (ultrasonic) sound waves.
Compressed liquids and gases, such as welding oxygen and acetylene, aviator’s breathing oxygen, nitrogen, and hydraulic accumulators, present another physical hazard to the aviation maintenance technician. Although some of these substances by themselves present hazards as chemical agents, placing them under pressure may create another unique hazard.
OSHA requires that areas where this exposure exists be clearly marked and that individuals exposed to these hazards be provided the proper safety equipment. In many cases this is easily accomplished, but in the aerospace industry particular concern should be paid to portable equipment that generates these hazards. Such equipment results in the potential for hazards to exist in areas where exposure is not usually a concern. X ray of aircraft structural parts is an example of such a situation. The aviation maintenance technician should remain conscious that potentially hazardous equipment is portable and remain vigilant for possible exposure in the work area.
Biological Hazards
Biological hazards, although not normally a major concern to the aviation maintenance technician, may occasionally exist in the work environment. Biological hazards are living organisms that may cause illness or disease. Some biological hazards also have toxic by-products. Typically, biological hazards are transmitted in the form of air droplets or spores and enter the body through contact with contaminated objects or individuals.
The practicing aviation maintenance technician in the workplace would most likely be exposed to biological hazards when working on cargo aircraft or in a cargo (baggage) compartment where breakage or leakage of biologically hazardous materials has occurred. FAA regulations require that the transportation of biologically hazardous materials be documented. When in doubt about the presence of such materials, the aviation maintenance technician should consult the aircraft’s record, possibly including the cargo manifest.
OSHA’S HAZARDOUS COMMUNICATIONS STANDARDS
In 1983, the first regulation requiring employers to advise employees of potentially hazardous materials in the work place was established. This standard, the Hazardous Communications Standard (29 CFR 1910.1200), was established by OSHA and has since been expanded to include almost all employers. The law requires that all employees and their supervisors be informed about the known hazards associated with the chemicals with which they work, regardless of the quantity of the chemicals involved in the operation. These requirements are part of the various right-to-know regulations. As part of these right-to-know regulations, employers are required to post a notice similar to that shown in Fig. 1-1.
FIGURE 1-1 Right-to-know poster.
There are five basic requirements of a hazard-communications program:
1. Inventory. An inventory (list) of all hazardous materials used within the workplace must be established and maintained.
2. Labeling. All hazardous chemicals shall be properly labeled.
3. Material safety data sheets (MSDSs). Material safety data sheets must be obtained for all material stored and/or used in the work area. A copy of these MSDSs must be maintained and made readily available to all employees during normal working hours. MSDSs provide detailed information concerning composition, health hazards, special handling instructions, and proper disposal practices for materials.
4. Training. All employees must be provided training regarding their rights under the right-to-know program, the proper handling of these materials, the labeling system used, and detection techniques.
5. Written program. Each employer must establish a written program that will comply with the four points just mentioned; this written program must be present at the work facility.
Material Safety Data Sheets
A material safety data sheet (MSDS) is a document provided by the material manufacturer or subsequent material processor that contains information related to the material hazard and includes safe handling and disposal procedures. The format of these sheets must be consistent with the requirements of the OSHA Hazard Communications Standard. MSDSs should be provided by the manufacturer for each hazardous material supplied by them. Normally MSDSs are provided with each shipment of a hazardous material. If one is not provided the technician should request one from the manufacturer. Most manufacturers post their MSDSs on their websites. Figure 1-2 is an example of a 16-section standardized MSDS. This format is used by most manufacturers.
FIGURE 1-2 Sample MSDS. (Sciencelab.com, Inc.)
The Occupational Safety and Health Administration (OSHA) specifies that certain information must be included on MSDSs, but does not require that any particular format be followed in presenting this information. OSHA recommends that MSDSs follow the 16-section format established by the American National Standards Institute (ANSI) for preparation of MSDSs.
By following this recommended format, the information of greatest concern to workers is featured at the beginning of the data sheet, including information on chemical composition and first aid measures. More technical information that addresses topics such as the physical and chemical properties of the material and toxicological data appears later in the document. While some of this information (such as ecological information) is not required by the Hazard Communication Standard (HCS), the 16-section MSDS is becoming the international norm.
As of June 1, 2015, MSDSs will be replaced by Safety Data Sheets (SDSs). The HCS will require chemical manufacturers, distributors, or importers to provide SDSs to communicate the hazards of hazardous chemical products. The new SDS will have a uniform format, and will include the section numbers, the headings, and associated information under the headings below:
Section 1: Identification includes product identifier; manufacturer or distributor name, address, phone number; emergency phone number; recommended use; restrictions on use.
Section 2: Hazard(s) Identification includes all hazards regarding the chemical; required label elements.
Section 3: Composition/Information on Ingredients includes information on chemical ingredients; trade secret claims.
Section 4: First-Aid Measures includes important symptoms/effects (acute, delayed); required treatment.
Section 5: Firefighting Measures lists suitable extinguishing techniques, equipment; chemical hazards from fire.
Section 6: Accidental Release Measures lists emergency procedures; protective equipment; proper methods of containment and cleanup.
Section 7: Handling and Storage lists precautions for safe handling and storage, including incompatibilities.
Section 8: Exposure Controls/Personal Protection lists OSHA’s Permissible Exposure Limits (PELs); Threshold Limit Values (TLVs); appropriate engineering controls; personal protective equipment (PPE).
Section 9: Physical and Chemical Properties lists the chemical’s characteristics.
Section 10: Stability and Reactivity lists chemical stability and possibility of hazardous reactions.
Section 11: Toxicological Information includes routes of exposure; related symptoms; acute and chronic effects; numerical measures of toxicity.
Section 12: Ecological Information*
Section 13: Disposal Considerations*
Section 14: Transport Information*
Section 15: Regulatory Information*
Section 16: Other Information includes the date of preparation or last revision.
Inventory
Even though many companies inventory the materials they use, a special inventory of hazardous materials must be maintained. Each item in the inventory should include the name of the hazardous material, location, and the approximate (or average) quantity in each area.
Materials sold in consumer form are not normally controlled. For example, if the aviation maintenance technician purchases a painted aluminum cover plate in a ready-to-install form, no MSDS would accompany the product. However, if the aviation maintenance technician purchases the aluminum sheet and paint separately, to fabricate the product, it is likely that an MSDS would accompany both the aluminum sheet and the paint.
Labeling
All hazardous materials should have identifying labels adhered to them. As a general rule, these labels should never be removed. In instances where materials are received in bulk form and transferred to small containers for use, two general rules apply. First, the container should be clearly labeled. Second, once a container is used for one hazardous substance, it should never be used to hold another substance.
Probably the most common standardized hazardous materials identification placard used today is that of the NFPA. Although this code is intended for the use of firefighters during a fire emergency, it is another tool available to the aviation maintenance technician that may be used to avoid hazardous situations. This placarding system uses four diamonds to form another diamond (Fig. 1-3). Each diamond position identifies the degree to which a particular type of hazard is present.
FIGURE 1-3 NFPA placard. (Copyright © 1990, National Fire Protection Association, Quincy, MA 02269. This warning system is intended to be interpreted and applied only by properly trained individuals to identify fire, health, and reactivity hazards of chemicals. The user is referred to a certain limited number of chemicals with recommended classifications in NFPA 49 and NFPA 325M, which would be used as a guideline only. Whether the chemicals are classified by NFPA or not, anyone using the 704 system to classify chemicals does so at his/her own risk.)
The top three diamonds follow a numbering system from 1 to 4, indicating the degree of hazard.
The topmost diamond specifies the relative fire hazard. The relative fire hazard is a function of the temperature at which the material will give off flammable vapors that will ignite when they come in contact with a spark or flame. This temperature is called the flash point. Figure 1-3 also shows how the number code is used to express the way in which the flash point ranges are specified.
The left side of the diamond specifies the health hazard and the right side of the diamond indicates the degree of the reactivity of the material.
The bottommost diamond indicates any specific hazard and, if more than one, the major hazard that applies to this material.
This diamond coding system may also use different colors to segregate each type of hazard.
The health hazard diamond is blue.
The flammability diamond is red.
The reactivity diamond is yellow.
The specific hazard diamond is white.
The aviation maintenance technician should be conscious of the environment in which work is being accomplished. For example, aviation maintenance technicians working in confined, poorly ventilated areas should use appropriate precaution if the NFPA health hazard code is greater than 0. Aviation maintenance technicians working on hot brakes or engines should beware of the relative fire hazard code.
Many companies have their own labeling program. In cases where codes are used, the company has the obligation to identify the coding system. An example of a labeling system used by Weber Marking Systems of Arlington Heights, IL, is shown in Fig. 1-4.
FIGURE 1-4 In-house labeling system. (Weber Marking Systems)
In-house labeling systems are most frequently used when the operations of the company require the transferring of hazardous materials from one container to another. In most cases, the in-house labeling is used in addition to the original container labels.
Generic in-house labeling systems are also available commercially. A commercially available hazardous materials identification system produced by Labelmaster, an American Labelmark Company, Chicago, IL, is shown in Fig. 1-5. As with most marking systems, the degree of hazard severity is based upon a numbering system. American also adds an index system using letters that correspond to the recommended personal protective equipment for use with the hazardous material.
FIGURE 1-5 Generic labeling system. (American Landmark Co.)
The majority of hazardous materials with which the aviation maintenance technician will come in contact are complex mixtures of chemicals. Normally, mixtures are analyzed as a whole to determine their physical properties and health hazards, if any exist. If a mixture has not been tested as a whole, it is to be considered hazardous if it contains more than 1 percent of any hazardous material. In the case of carcinogens, the minimum component amount is 0.1 percent.
DISPOSAL AND ACCIDENTAL RELEASES OF HAZARDOUS MATERIALS
Just as the Occupational Safety and Health Act was enacted to protect the health of industrial workers, the National Environmental Policy Act of 1969 (NEPA) was enacted to protect the environment. The NEPA established the Environmental Protection Agency (EPA) to accomplish its objectives.
Businesses that use hazardous materials must be conscious of the hazards, not only while using the materials but also when disposing of them. As part of the employee’s orientation to hazardous materials, proper disposal techniques should be addressed.
Creators of hazardous waste are responsible for the identification, separation, labeling, packaging, storage, shipping, and disposal of the waste produced. The EPA monitors the movement of hazardous waste from the time it is generated to the time it reaches a licensed treatment, storage, and disposal facility (TSDF).
As part of this process, generators of hazardous waste must maintain detailed records regarding hazardous-waste materials. It is therefore extremely important that the aviation maintenance technician comply with the record-keeping practices and procedures of the company.
Routine handling of hazardous materials is typically not a problem for the aviation maintenance technician because the technician either is familiar with the procedure or has time during which specific instruction may be obtained. Accidental release of hazardous materials, however, is another story.
When an accidental release occurs, the typical reaction is one of panic. As part of the employer training sessions, the aviation maintenance technician will receive instructions regarding procedures to follow in case of an accidental release, but these may not be remembered, particularly when an emergency occurs.
Accidental releases most typically occur when the hazardous material is in a liquid or gaseous state. It is important that the aviation maintenance technician not equate hazardous materials with rarely used materials. Spillage of commonly used hazardous materials such as aviation fuels and lubricants is also considered an accidental release of a hazardous material.
Accidental releases, by definition, do not happen because they are planned. However, because of their potential impact, the aviation technician should plan for and anticipate their occurrence. Prior to using a hazardous material, the aviation maintenance technician should evaluate the types of accidental releases that might occur and prepare for them. A review of the MSDS prior to usage is advised.
The aviation maintenance technician should be concerned first with personal safety. If a release might have detrimental effect on other individuals, a means of notification should be established. Containment is the next priority. This may take a little imagination. For example, if the hazardous materials are in a tank, how could a leak be stopped? If a drain shutoff value was dislodged, how could the drain be quickly plugged?
The EPA has established reporting procedures for accidental release of hazardous materials. Whether an accidental release needs to be reported is determined by the quantity or concentration of material released. Calculations of concentration may be rather complex and typically are beyond the capability of the technician. Therefore, all accidental releases should be reported to the aviation maintenance technician’s supervisor as soon as possible. Any information the aviation maintenance technician has regarding the amount released should be noted and submitted to the supervisor.
REVIEW QUESTIONS
1. What are the three general categories of hazardous materials?
2. What are the four classes of chemical agents?
3. How long does it take for a toxic agent to show its effects on the human body?
4. What types of chemical agents typically require the use of personal protective equipment designed to limit direct body contact?
5. List some of the flammable materials found in the aviation industry.
6. What type of corrosives generally come in powder form?
7. What type of corrosives generally come in liquid form?
8. How long does it take toxins to dissipate from the human body?
9. What type of toxin may cause cancer?
10. What happens when chloride bleach and ammonia are mixed?
11. To what document should the aviation maintenance technician refer regarding the potential hazards when dealing with hazardous materials?
12. Why are physical hazards not always easy to avoid?
13. In what form are biological hazards most likely to be transmitted?
14. What requires that an employee be informed about the presence of hazardous materials in the workplace?
15. What are the five basic requirements of a hazard-communications program?
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