Block 4 SGWB Student 2021 Final-pages-1.pdf

Study Guide Workbook Block IV: Chemical Controls B3ABY4B031-0A1B Technical Training Bioenvironmental Engineering Apprentice Course 6 January 2020 INSTRUCTOR COPY Supersedes: None 711th HUMAN PERFORMANCE WING US Air Force School of Aerospace Medicine Wright-Patterson AFB, Ohio DESIGNED FOR OFFICIA...

Study Guide Workbook Block IV: Chemical Controls B3ABY4B031-0A1B Technical Training Bioenvironmental Engineering Apprentice Course 6 January 2020 INSTRUCTOR COPY Supersedes: None 711th HUMAN PERFORMANCE WING US Air Force School of Aerospace Medicine Wright-Patterson AFB, Ohio DESIGNED FOR OFFICIAL COURSE USE ONLY Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B TABLE OF CONTENTS Block IV - Unit 1: Control Options ...................................................................................... 6 Objective 1a: List chemical threat control options. .................................................................. 6 Hierarchy of Controls ...................................................................................................................... 6 Engineering Controls ...................................................................................................................... 7 Administrative Controls ................................................................................................................... 7 Personal Protective Equipment (PPE)............................................................................................ 8 Block IV – Unit 2: Substance-Specific Standards and Regulated Areas ......................... 9 Objective 2a: Recall OSHA substance-specific standards and the conditions that are required for establishing a regulated area............................................................................... 9 Substance-Specific Standards ....................................................................................................... 9 Regulated Areas ........................................................................................................................... 10 Block IV- Unit 3: Protective Clothing Concepts ............................................................... 13 Objective 3a: Understand the use and selection of protective clothing................................. 13 Types of Protective Clothing......................................................................................................... 13 Physiological Effects ..................................................................................................................... 14 Objective 3b: Understand basic concepts of protective clothing. .......................................... 15 Chemical Permeation ................................................................................................................... 15 Breakthrough Time ....................................................................................................................... 15 Degradation .................................................................................................................................. 15 Penetration ................................................................................................................................... 16 Block IV – Unit 4: Introduction to Ventilation ................................................................... 17 Objective 4a: State the basic industrial ventilation system principles. .................................. 17 Key Concepts and Definitions ...................................................................................................... 17 Components of a Ventilation System ........................................................................................... 19 Duct Area and Volumetric Flow Rate Calculations....................................................................... 20 Characteristics of Static Pressure, Velocity Pressure, and Total Pressure.................................. 22 Types of Pressure Losses and Their Causes .............................................................................. 25 Make-Up Air .................................................................................................................................. 27 Block IV – Unit 5: Dilution Ventilation ............................................................................... 28 Objective 5a: State basic principles associated with dilution ventilation. .............................. 28 Definitions ..................................................................................................................................... 28 Factors in Selecting Dilution Ventilation ....................................................................................... 30 Advantages and Disadvantages ................................................................................................... 30 Dilution Ventilation Equations ....................................................................................................... 31 Survey Equipment ........................................................................................................................ 33 2 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Block IV – Unit 6: Local Exhaust Ventilation .................................................................... 35 Objective 6a: Identify types and basic principles of local exhaust ventilation (LEV) systems. ................................................................................................................................ 35 Local Exhaust Ventilation (LEV) Systems .................................................................................... 35 Advantages and Disadvantages ................................................................................................... 35 Types of Hoods............................................................................................................................. 37 Design Parameters and References ............................................................................................ 38 Block IV – Unit 7: Ventilation Survey Requirements ....................................................... 40 Objective 7a: List ventilation survey requirements. ............................................................... 40 Types of Surveys .......................................................................................................................... 40 Survey Equipment ........................................................................................................................ 42 Block IV – Unit 8: Pitot Traverse Surveys ......................................................................... 45 Objective 8a: Given references, survey equipment, and a ventilation system, perform a pitot traverse ventilation survey and static pressure check IAW PT-IV-8a. .................................. 45 Survey Materials and Equipment.................................................................................................. 45 Pitot Traverse Survey Steps ......................................................................................................... 45 Objective 8b: Given ventilation survey data and references, perform ventilation calculations IAW PT-IV-9b. ....................................................................................................................... 48 Calculations .................................................................................................................................. 48 Block IV– Unit 9: Face and Capture Surveys.................................................................... 50 Objective 9a: Given a ventilation system, survey equipment, and references, perform face and capture ventilation surveys IAW PT IV-9a...................................................................... 50 Survey Materials and Equipment.................................................................................................. 50 Face Velocity Survey Steps .......................................................................................................... 50 Capture Velocity Survey Steps ..................................................................................................... 51 Objective 9b: Given ventilation survey data and references, perform ventilation calculations IAW PT IV-9b. ....................................................................................................................... 52 Calculations .................................................................................................................................. 52 Block IV – Unit 10: Ventilation Follow-Up ......................................................................... 61 Objective 10a: Identify basic follow-up actions for deficient ventilation systems. ................. 61 Deficiency Identification ................................................................................................................ 61 Troubleshooting and Repair ......................................................................................................... 61 Additional Surveys ........................................................................................................................ 63 Responsibilities ............................................................................................................................. 63 Block IV – Unit 12: Respiratory Protection Program ....................................................... 65 Objective 12a: Identify roles and responsibilities of BE, the program administrator, workplace supervisor, and the worker in the Respiratory Protection Program (RPP). ........................... 65 Introduction and Guidance ........................................................................................................... 65 Responsibilities ............................................................................................................................. 66 3 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Block IV – Unit 13: Respirators .......................................................................................... 68 Objective 13a: Recall the operating principles, types and components of respirators. ......... 68 Definitions ..................................................................................................................................... 68 Types of Respirators .................................................................................................................... 70 Major Components of a Respirator and Their Function ............................................................... 72 Categories of Respiratory Protection............................................................................................ 73 Types of Filters and Cartridges .................................................................................................... 74 Advantages and Disadvantages of Respirator Types .................................................................. 75 Block IV – Unit 14: Care and Maintenance of Respirators .............................................. 77 Objective 14a: Recall the care and maintenance of respirators............................................ 77 Cleaning and Sanitizing Respirators ............................................................................................ 77 Inspection and Storage Requirements ......................................................................................... 78 Block IV – Unit 15: Respirator Selection ........................................................................... 80 Objective 15a: Given a respiratory selection form and instructor guidance, identify how to select an appropriate respirator IAW PT IV-15a. .................................................................. 80 Selection of Respirators ............................................................................................................... 80 Block IV – Unit 16: Respiratory Protection Program Evaluation .................................... 84 Objective 16a: Describe the procedures for evaluating the workplace Respiratory Protection Program. ............................................................................................................................... 84 Respiratory Protection Program Elements ................................................................................... 84 Evaluating Shops .......................................................................................................................... 85 Medical Evaluations ...................................................................................................................... 85 Block IV – Unit 17: Respirator Fit Testing......................................................................... 86 Objective 17a: Given references, respirators, and supplies, perform qualitative fit testing IAW PT IV-17a. ..................................................................................................................... 86 Performing Qualitative Fit testing ................................................................................................. 86 Equipment and Supplies ............................................................................................................... 86 Sensitivity Test Procedures .......................................................................................................... 87 Qualitative Fit testing Procedures................................................................................................. 88 Objective 17b: Given references, respirators, and supplies, perform quantitative fit testing IAW PT IV-17b. ..................................................................................................................... 89 Purpose of Performing Quantitative Fit testing............................................................................. 89 Equipment and Supplies ............................................................................................................... 89 The Portacount System ................................................................................................................ 91 Quantitative Fit Test Procedures .................................................................................................. 91 Quantitative Fit Test Methods....................................................................................................... 93 TABLE OF FIGURES Figure 1: Hierarchy of Controls ............................................................................................... 6 Figure 2: Permeation............................................................... Error! Bookmark not defined. Figure 3: Components of a Ventilation System ..................................................................... 19 Figure 4: Volumetric Flowrate Triangle ................................................................................. 21 Figure 5: Static Pressure....................................................................................................... 23 4 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Figure 6: Velocity Pressure ................................................................................................... 23 Figure 7: Total Pressure........................................................................................................ 24 Figure 8: Vena Contracta for Different Hood Types .............................................................. 27 Figure 9: Supply Vs. Exhaust Air Flow .................................................................................. 29 Figure 10: Negative and Positive Pressure ........................................................................... 29 Figure 11: Smoke Tubes ....................................................................................................... 33 Figure 12: Magnehelic Gauge ............................................................................................... 34 Figure 13: Balometer............................................................................................................. 34 Figure 14: Local Exhaust Ventilation..................................................................................... 35 Figure 15: Laboratory Hood .................................................................................................. 37 Figure 16: Band Saw with Capture Hood .............................................................................. 37 Figure 17: Industrial Ventilation: A Manual of Recommended Practice for Design, 30th Edition ................................................................................................................................... 38 Figure 18: Ventilation Pre-Survey Form ................................................................................ 39 Figure 19: Thermoanemometer ............................................................................................ 42 Figure 20: Pitot Traverse Measurement Points..................................................................... 43 Figure 21: Pitot Tube............................................................................................................. 43 Figure 22: Inclined Manometer ............................................................................................. 44 Figure 23: Round Duct Traverse Points ................................................................................ 46 Figure 24: Pitot Traverse Survey Form. Static Pressure and Velocity Pressure Highlighted. .............................................................................................................................................. 47 Figure 25: Pitot Traverse Survey Form. Velocity Highlighted. .............................................. 49 Figure 26: Rectangular Hood ................................................................................................ 50 Figure 27: Circular Hood ....................................................................................................... 50 Figure 28: Face Sectioning - Circular Hood .......................................................................... 51 Figure 29: Face Sectioning - Rectangular Hood ................................................................... 51 Figure 30: Face Velocity Method Pre-Survey Form (Front) .................................................. 53 Figure 31: Face Velocity Method Pre-Survey Form (Back)................................................... 54 Figure 32: Face Velocity Method Survey Form (Front) ......................................................... 55 Figure 33: Face Velocity Method Survey Form (Back) ......................................................... 56 Figure 34: Face Velocity Method Pre-Survey Form (Front) .................................................. 57 Figure 35: Face Velocity Method Pre-Survey Form (Back)................................................... 58 Figure 36: Face Velocity Method Survey Form (Front) ......................................................... 59 Figure 37: Face Velocity Method Survey Form (Back) ......................................................... 60 Figure 39: Negative-Pressure Air Purifying Respirators ....................................................... 71 Figure 38: Powered Air Purifying Respirator ......................................................................... 71 Figure 40: Airline Respirator ................................................................................................. 72 Figure 41: Self-Contained Breathing Apparatus (SCBA) ...................................................... 72 Figure 42: Filtering Facepiece Device (FFPD) ...................................................................... 73 Figure 43: P100 Particulate Filter.......................................................................................... 74 Figure 44: Organic Vapor Cartridge ...................................................................................... 75 Figure 45: P100/Organic Vapor Cartridge............................................................................. 75 Figure 46: Fit Test Hood ....................................................................................................... 86 Figure 47: Nebulizers ............................................................................................................ 86 Figure 48: Portacount Pro System ........................................................................................ 90 Figure 49: Wick Assembly..................................................................................................... 90 5 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Unit 1: Control Options BLOCK IV - UNIT 1: CONTROL OPTIONS Objective 1a: List chemical threat control options. Chemicals can be safely stored, handled, and used if the hazards are fully understood and the necessary hazard controls are in place. The objective of chemical controls is to ensure that exposure to harmful chemicals does not result in occupational illness. The type of control measures instituted depend on the nature of the hazard and its routes of entry into the body. HIERARCHY OF CONTROLS A hierarchy of controls is used as a means of determining how to implement feasible and effective control solutions. It ranks control measures in the order of their effectiveness and stresses the elimination of the hazards as preferable to the use of personal protective equipment (PPE). The methods of control of health hazards in the workplace are divided into three categories: Engineering, Administrative and PPE. The Figure 1 is a representation of the hierarchy of controls: Figure 1: Hierarchy of Controls The control methods at the top are preferred over those at the bottom because they do not rely on the worker to be effective. Following this hierarchy normally leads to the implementation of safer processes, where the risk of overexposure has been substantially reduced. 6 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Unit 1: Control Options ENGINEERING CONTROLS Engineering controls are favored over administrative controls and PPE because they remove the hazard before it becomes in contact with the worker. Well-designed engineering controls can be highly effective in protecting workers and will typically not be dependent on worker interactions to achieve a high level of protection. SUBSTITUTION Substitution refers to the replacement of a hazardous material or activity with one that is less hazardous (e.g., the replacement of mercury thermometers with alcohol thermometers or dip coating materials rather than spray coating to reduce the inhalation hazard). MINIMIZATION Minimization is the expression used when a hazard is lessened by scaling down the hazardous process. Hence, the quantity of hazardous materials used and stored is reduced, lessening the potential hazards. ISOLATION Isolation is the term applied when a barrier is interposed between a material, equipment, or process hazard and the property or persons who might be affected by the hazard (e.g., glove box, blast shield). VENTILATION Ventilation is a method of controlling the work environment by strategically supplying (adding) or exhausting (removing) air. The two types of ventilation are local exhaust and general or dilution ventilation. Local exhaust systems are designed to catch the contaminated air at or near the source and remove it from the area before it reaches the workers breathing zone. General or dilution ventilation attempts to control hazardous atmospheres by diluting the atmosphere to a safe level by either exhausting or supplying air to the area. ADMINISTRATIVE CONTROLS Administrative controls are frequently used with existing processes where hazards are not particularly well controlled. They consist of managerial efforts to reduce hazards through planning, training, job rotation, reduction of exposure time and written policies and procedures. These methods for protecting workers have proven to be less effective than engineering controls, requiring significant effort by the affected workers. 7 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Unit 1: Control Options PERSONAL PROTECTIVE EQUIPMENT (PPE) When engineering and administrative controls cannot adequately control chemical hazards, PPE must be considered. PPE includes a wide variety of items worn by a worker to isolate them from chemical hazards. PPE is considered the last resort of protection, creating a physical barrier at the point of exposure. It includes articles to protect the eyes, skin, and the respiratory system (e.g., goggles, face shields, coats, gloves, aprons, respirators). The effectiveness of PPE is highly dependent on the user. Some items of PPE may be perceived as cumbersome and uncomfortable to wear so workers may resist using it or use it improperly. 8 Bioenvironmental Engineering Apprentice B3ABY4B031-0A1B Block IV: Chemical Controls Unit 2: Substance-Specific Standards and Regulated Areas BLOCK IV – UNIT 2: SUBSTANCE-SPECIFIC STANDARDS AND REGULATED AREAS Objective 2a: Recall OSHA substance-specific standards and the conditions that are required for establishing a regulated area. Last block, you learned that many factors come into play in determining if a chemical is considered hazardous. Some of these factors to consider are whether or not the chemical is flammable, corrosive, reactive, or toxic. Other factors to consider include the physical form of the chemical (solid, liquid, gas, or vapor) and how the chemical enters the worker’s body. An important step in determining the potential of a chemical to cause adverse effects to a person is to conduct a health risk assessment, which includes taking air samples to determine the airborne exposure levels of the chemical. In some cases you may be sampling for chemicals where additional protection measures are needed to protect workers. OSHA has established substance-specific standards for these chemicals. Some of these standards require the establishment of what is known as a regulated area. SUBSTANCE-SPECIFIC STANDARDS There are thousands of chemicals that are considered potentially hazardous if they are absorbed or enter a person’s body. For many of these chemicals, OSHA established Permissible Exposure Limits (PELs) that should be adequate to protect most workers. However, for some chemicals, adherence to the PEL might not be enough. For those chemicals, where additional protection measures are needed to protect workers, OSHA has developed substance-specific standards (sometimes referred to as expanded standards). These standards address specific actions that must be taken when workers handle these chemicals. Most of OSHA’s substance-specific standards that you will deal with are found in the OSHA General Industry Standard (1910 series, Subpart Z). OSHA’s Construction Industry Standard (1926 series, Subpart Z) also contains chemicals that have substance standards, but you will rarely deal with them due to the nature of work done in the Air Force. Below is a listing of the current OSHA General Industry substance-specific standards: • • • • • • • • • • • • • 1910.1001 - Asbestos 1910.1002 - Coal tar pitch volatiles 1910.1003 - 13 Carcinogens (4Nitrobiphenyl, etc.) 1910.1004 - alpha-Naphthylamine 1910.1006 - Methyl chloromethyl ether 1910.1007 - 3,'-Dichlorobenzidine 1910.1008 - bis-Chloromethyl ether 1910.1009 - beta-Naphthylamine 1910.1010 – Benzidine 1910.1011 - 4-Aminodiphenyl 1910.1012 - Ethyleneimine 1910.1013 - beta-Propiolactone 1910.1014 - 2-Acetylaminofluorene • • • • • • • • • • • • 9 1910.1015 - 4-Dimethylaminoazobenzene 1910.1016 - N-Nitrosodimethylamine 1910.1017 - Vinyl chloride 1910.1018 - Inorganic arsenic 1910.1024 - Beryllium 1910.1025 - Lead 1910.1026 - Chromium (VI) 1910.1027 - Cadmium 1910.1028 - Benzene 1910.1029 - Coke oven emissions 1910.1030 - Bloodborne pathogens 1910.1043 - Cotton dust Bioenvironmental Engineering Apprentice B3ABY4B031-0A1B Block IV: Chemical Controls Unit 2: Substance-Specific Standards and Regulated Areas • • • • 1910.1044 - 1,2-dibromo-3chloropropane 1910.1045 - Acrylonitrile 1910.1047 - Ethylene oxide 1910.1048 - Formaldehyde • • • • 1910.1050 - Methylenedianiline 1910.1051 - 1,3-Butadiene 1910.1052 - Methylene Chloride 1910.1053 - Respirable Crystalline Silica Below are some examples of workplaces on a base where you can expect to find some of these chemicals: • • • • • • • • • • Medical laboratory (formaldehyde) Vehicle maintenance (asbestos) Fuels/Fuels lab/Fuel system repair (benzene) Avionics (methylene chloride) Asbestos abatement teams Shops that spray/remove primers (chromium VI) Shops that use adhesives/epoxies (formaldehyde) Shops that perform welding/brazing (chromium VI/cadmium) Medical hospital/Clinic (blood borne pathogens) CE Horizontal Maintenance (crystalline silica) Depending on the chemical you are researching, OSHA’s substance-specific standards contain all or some of the following information/requirements: • • • • • • • • • • Applicable permissible exposure limits Exposure monitoring Establishment of a regulated area Methods of compliance Control methods (engineering, work practice, PPE) Warning signs (verbiage and location) Worker training Worker notification Recordkeeping Documentation Some requirements must only be implemented/adhered to if air sampling results indicate exposure levels greater than the established PEL. REGULATED AREAS OSHA has established substance-specific standards for certain chemicals that require specific protective measures for these specific substances. Some of these standards require the establishment of what is known as a regulated area. A regulated area limits access to a work area where specific hazardous chemicals/materials exceed allowable exposure limits (PEL, TWA, action limit, etc.) as stated in the relevant standard. 10 Bioenvironmental Engineering Apprentice B3ABY4B031-0A1B Block IV: Chemical Controls Unit 2: Substance-Specific Standards and Regulated Areas Some examples of substance-specific standards requiring a regulated area when exposures exceed a certain level are: • • • • • • • • • 1910.1001 - Asbestos 1910.1017 - Vinyl Chloride 1910.1024 - Beryllium 1910.1026 - Chromium (VI) 1910.1027 - Cadmium 1910.1028 - Benzene 1910.1048 - Formaldehyde 1910.1052 - Methylene Chloride 1910.1053 - Respirable Crystalline Silica Some general requirements for a regulated area include: • • • • • • The area must be clearly identified (warning signs posted) at all entrances and made known to all workers who work in or adjacent to the area. The area must be delineated and segregated from the rest of the work area in a manner that minimizes/limits the number of workers who will be exposed to the specific chemical. The area must have access controlled by either administrative or physical means. The supervisor must ensure that workers do not eat, drink, smoke, chew tobacco or gum, or apply cosmetics in regulated areas. The regulated area must be established and maintained according to the criteria of the OSHA substance-specific standard. Workers potentially exposed to a substance with a specific standard must be monitored and protected IAW that specific standard. It is important to remember that each substance-specific standard must be reviewed to determine the criteria that must be followed if a regulated area must be established—although some standards might list similar criteria, you must thoroughly read through the OSHA standard for specific criteria relevant to the chemical(s) of concern. For example, some of the standards listed above include specific wording that must be included on regulated area warning signs. To help you get a better idea of the requirements of a regulated area, consider the following scenario involving one of the OSHA substance-specific standards, formaldehyde. 11 Bioenvironmental Engineering Apprentice B3ABY4B031-0A1B Block IV: Chemical Controls Unit 2: Substance-Specific Standards and Regulated Areas Scenario: The medical group where you are assigned has a medical laboratory where workers are occupationally exposed to formaldehyde when performing a variety of specimen collection, analysis, and preservation tasks. You conducted air sampling during several activities when a maximum risk worker was using formaldehyde throughout the workday. The sample results indicate the worker was exposed to airborne formaldehyde levels exceeding the short-term exposure limit (STEL) but not the 8-hr Time-Weighted Average (TWA) Permissible Exposure Limit (PEL). While researching OSHA 29 CFR 1910.1048, you read the following information concerning regulated areas: 1910.1048(e)(1)(i) The employer shall establish regulated areas where the concentration of airborne formaldehyde exceeds either the TWA or the STEL and post all entrances and access ways with signs bearing the following legend: DANGER FORMALDEHYDE MAY CAUSE CANCER CAUSES SKIN, EYE, AND RESPIRATORY IRRITATION AUTHORIZED PERSONNEL ONLY 1910.1048(e)(2) The employer shall limit access to regulated areas to authorized persons who have been trained to recognize the hazards of formaldehyde. 1910.1048(e)(3) An employer at a multiemployer worksite who establishes a regulated area shall communicate the access restrictions and locations of these areas to other employers with work operations at that worksite. In this scenario, you were told that the STEL had been exceeded. According to 1910.1048, Formaldehyde, a regulated area must be established when concentrations exceed the STEL. The formaldehyde standard also states that the regulated area signs must have specific wording, the area must be limited to only authorized personnel with training, and access restrictions must be communicated to others who work in the area. 12 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Unit 3: Protective Clothing Concepts BLOCK IV- UNIT 3: PROTECTIVE CLOTHING CONCEPTS Objective 3a: Understand the use and selection of protective clothing. Dermatological disorders are one of the NIOSH’s top 10 leading occupational health problems. These disorders are primarily a result of unprotected exposures to harmful chemical, biological, and physical agents. Most of the injuries and disease risks from dermatological disorders can be prevented or reduced through the appropriate selection and use of protective clothing. Although protective clothing can be an effective control method for occupational hazards, its effectiveness depends on proper use by the wearer. Protective clothing failure, in addition to its improper selection and use can result in injury or illness. TYPES OF PROTECTIVE CLOTHING Protective clothing in a generic sense includes all elements of a protective ensemble (e.g., garments, gloves, boots, etc.). Thus, protective clothing can include everything from a finger cot providing protection against paper cuts, to a fully encapsulating suit with self-contained breathing apparatus used for an emergency response to a hazardous chemical spill. Protective clothing material and configurations vary greatly depending on the intended use. It can be made of natural materials (e.g., cotton, wool, leather), man-made fibers (e.g., nylon, rayon), or various polymers (plastics and rubbers such as butyl rubber, polyvinyl chloride, and chlorinated polyethylene). The protective material used should be based on the particular chemicals being used. Table 1 summarizes by hazard common performance requirements of protective clothing materials. Hazard Table 1: Common PPE Performance Characteristics and Materials Thermal Performance Characteristic Required Insulation Vibration Damping Chemical/Toxicological Permeation resistant Biological Fluid proof; Puncture resistant Usually fluid or particle resistant Radiological Common Protective Materials Heavy cotton or other natural fabrics Rubber gloves with elastomeric linings Rubber material; Elastomeric materials Rubber material Rubber gloves; Lead lined, resistant for radionuclides, or shield containing Gloves Protective gloves are made from a wide variety of natural and synthetic materials. Light-duty cotton gloves and heavy-duty leather gloves are used to protect against a variety of physical hazards. Synthetic gloves can be used to protect against both physical and chemical hazards. 13 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Unit 3: Protective Clothing Concepts Chemically protective gloves usually are available in a wide variety of polymers, rubbers, and material combinations such as polymer coated cotton gloves. Boots Boots are available in a wide variety of lengths ranging from hip length to those that cover only the bottom of the foot. Chemical protective boots are available in only a limited number of polymers since the boot heal and sole require a high degree of wear resistance. Common polymers and rubbers used in chemically resistant boot construction include PVC (polyvinyl chloride), butyl rubber, nitrile rubber, and neoprene rubber. Garments Chemical protective garments may come as one-piece, fully encapsulating, gas-tight garments with attached gloves and boots or as separate components (e.g., pants, jacket, hoods, etc.). Some suits use layering of different polymers to improve the range of chemical resistance (e.g., layers of neoprene, nylon, and butyl rubber). PHYSIOLOGICAL EFFECTS Heat stress is the net heat load to which a worker may be exposed from the combined contributions of metabolic heat, environmental factors, and clothing requirements. Mild or moderate heat stress may cause discomfort and may adversely affect performance and safety, but it is not harmful to health. As the heat stress approaches human tolerance limits, the risk of heat-related disorders increases. Ideally, free movement of cool, dry air over the skin’s surface maximizes heat removal by both evaporation and convection. Evaporation of sweat from the skin is the predominant heat removal mechanism. Water-vapor-impermeable and thermally insulating clothing, as well as encapsulating suits and multiple layers of clothing, severely restrict heat removal. With heat removal hampered by clothing, metabolic heat buildup may produce excessive heat strain even when ambient conditions are considered cool. 14 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Unit 3: Protective Clothing Concepts Objective 3b: Understand basic concepts of protective clothing. CHEMICAL PERMEATION Permeation is the process by which a chemical moves through a material at the molecular level. Individual chemical molecules enter the material and pass between the molecules of the protective clothing. Sometimes, permeation occurs without any physical changes to the material (such as swelling or cracking), so the clothing may seem unaffected, even though it has been compromised and does not provide adequate protection. Figure 2 depicts the molecules of a contaminant passing through the molecules of the protective garment. Figure 2: Permeation For permeation to occur, continuous contact between the chemical and the material is not required. Intermittent exposures can also result in significant permeation. BREAKTHROUGH TIME Breakthrough time is how much time it takes from the initial contact of the chemical with the material until it is detected on the opposite side of the material (essentially, when it begins to soak through). The greater the breakthrough time, the more protective the material is for that particular chemical. DEGRADATION Degradation is a change in one or more physical properties of a protective material caused by contact with a chemical. Latex rubber, which is widely used for medical gloves, is readily soluble in toluene and hexane. Therefore, latex or natural rubber gloves would be ineffective for protection against these chemical solvents. Degradation also includes material swelling, stiffening, wrinkling, changing color, and other physical deterioration. 15