Block 4 Unit 3 pdf.pdf

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 leadin...

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 Bioenvironmental Engineering Apprentice Block IV: Chemical Controls B3ABY4B031-0A1B Unit 3: Protective Clothing Concepts PENETRATION Penetration is the flow of a chemical through zippers, weak seams, pinholes, cuts, or imperfections in the protective clothing on a nonmolecular level. Even the best protective barriers are rendered ineffective if punctured or torn. 16