The purpose of chemical protective clothing and equipment is to shield or isolate individuals from the chemical, physical, and biological hazards that may be encountered during hazardous materials operations. During chemical operations, it is not always apparent when exposure occurs. Many chemicals pose invisible hazards and offer no warning properties.
These guidelines describe the various types of clothing that are appropriate for use in various chemical operations, and provides recommendations in their selection and use. Protective clothing is used mainly to prevent exposure of activities. These hazards can be grouped into categories such as chemical, thermal, nuclear, radiation (X-rays, UV) and biological hazards.
DESCRIPTIONS.
A.THE CLOTHING ENSEMBLE.
The approach in selecting personal protective clothing must encompass an "ensemble" of clothing and equipment items which are easily integrated to provide both an appropriate level of protection and still allow one to carry out activities involving chemicals. In many cases, simple protective clothing by itself may be sufficient to prevent chemical exposure, such as wearing gloves in combination with a splash apron and face shield (or safety goggles).
1.The following is a checklist of components that may form the chemical protective ensemble:
Protective clothing (suit, coveralls, hoods, gloves, boots);
Respiratory equipment (SCBA, combination SCBA/SAR, air purifying respirators);
Cooling system (ice vest, air circulation, water circulation);
Communications device;
Head protection;
Eye protection;
Ear protection;
Inner garment; and
Outer protection (overgloves, overboots, flashcover).
B.ENSEMBLE SELECTION FACTORS.
1.Chemical Hazards.
Chemicals present a variety of hazards such as toxicity, corrosiveness, flammability, reactivity, and oxygen deficiency. Depending on the chemicals present, any combination of hazards may exist.
2.Physical Environment.
Chemical exposure can happen anywhere: in industrial settings, on the highways, or in residential areas. It may occur either indoors or outdoors; the environment may be extremely hot, cold, or moderate; the exposure site may be relatively uncluttered or rugged, presenting a number of physical hazards; chemical handling activities may involve entering confined spaces, heavy lifting, climbing a ladder, or crawling on the ground. The choice of ensemble components must account for these conditions.
3.Duration of Exposure.
The protective qualities of ensemble components may be limited to certain exposure levels (e.g. material chemical resistance, air supply). The decision for ensemble use time must be made assuming the worst case exposure so that safety margins can be applied to increase the protection available to the worker.
4.Protective Clothing or Equipment Available.
Hopefully, an array of different clothing or equipment is available to workers to meet all intended applications. Reliance on one particular clothing or equipment item may severely limit a facility's ability to handle a broad range of chemical exposures. In its acquisition of equipment and clothing, the safety department or other responsible authority should attempt to provide a high degree of flexibility while choosing protective clothing and equipment that is easily integrated and provides protection against each conceivable hazard.
Heart Rate
Count the radial pulse during a 30-second period as early as possible in any rest period. If the heart rate exceeds 110 beats per minute at the beginning of the rest period, the next work cycle should be shortened by one-third.
Oral Temperature
Do not permit an end user to wear protective clothing and engage in work when his or her oral temperature exceeds 100.6 F (38.1C).
Use a clinical thermometer (three minutes under the tongue) or similar device to measure oral temperature at the end of the work period (before drinking), as follows:
If the oral temperature exceeds 99.6F (37.6C), shorten the next work period by at least one-third.
If the oral temperature exceeds 99.6F (37.6C) at the beginning of a response period, shorten the mission time by one-third.
Body Water Loss
Measure the end user's weight on a scale accurate to plus or minus 0.25 pounds prior to any response activity. Compare this weight with his or her normal body weight to determine if enough fluids have been consumed to prevent dehydration. Weights should be taken while the end user wears similar clothing, or ideally, in the nude. The body water loss should not exceed 1.5% of the total body weight loss from a response.
CONCLUSION
Extensive research is going on in this area of protective clothing especially in protective clothing against pesticides. Several workers have studied effect of water repellent finishes. Statistical models have been developed to predict pesticide penetration through woven as well as non-woven chemical protective clothing.
Fabric characteristics such as fibre content, fabric construction, type of fabric and type of finishing can affect the barrier properties of protective clothing. It has been studied that pesticide absorption by finished fabric is less than unfinished fabric.
The effect of layered clothing on penetration of pesticides was studied. It has been observed that single layers of heavy weight denim acted as a trap allowing little pesticide to pass through, while the thinner fabrics were easily penetrated. In the two layer fabrics, penetration was reduced by the presence of the second layer of fabric, while the air permeability remained unchanged.
Other works are being conducted to examine different materials and finishes for their barrier effectiveness against commonly used pesticides.
BIBLIOGRAPHY
Barker, R.L. and Coletta, G.C. 1986. performance of protective clothing. American Societyfor testing materials: Philadelphia.
Forsberg, K. and Keith, L.H. 1989. Chennai protective clothing performance index.
Book. John wiley & sons: New York
Forsberg, K. and mansdrof, S.Z. 1989, quick selection guide to chemical protective clothing. Van nostrand-reinhold: New York
About Author:
Mr. Saurabh Jain & Mr. Pawan Patel are Final Year Student of Textile Technology, S.V.I.T.S. Indore (M.P.)
To read more articles on Textile, Fashion, Apparel, Technology, Retail and General please visit www.fibre2fashion.com/industry-article
STORAGE
Clothing must be stored properly to prevent damage or malfunction from exposure to dust, moisture, sunlight, damaging chemicals, extreme temperatures and impact. Procedures are needed for both initial receipt of equipment and after use or exposure of that equipment. Many manufacturers specify recommended procedures for storing their products. These should be followed to avoid equipment failure resulting from improper storage.
Some guidelines for general storage of chemical protective clothing include:
Potentially contaminated clothing should be stored in an area separate from street clothing or unused protective clothing.
Potentially contaminated clothing should be stored in a well-ventilated area, with good air flow around each item, if possible.
Different types and materials of clothing and gloves should be stored separately to prevent issuing the wrong material by mistake (e.g. many glove materials are black and cannot be identified by appearance alone).
Protective clothing should be folded or hung in accordance with manufacturer instructions.
MAINTENANCE
Manufacturers frequently restrict the sale of certain protective suit parts to individuals or groups who are specially trained, equipped, or authorized by the manufacturer to purchase them. Explicit procedures should be adopted to ensure that the appropriate level of maintenance is performed only by those individuals who have this specialized training and equipment. In no case should you attempt to repair equipment without checking with the person in your facility who is responsible for chemical protective clothing maintenance.
The following classification scheme is recommended to divide the types of permissible or nonpermissible repairs:
Level 1: User or wearer maintenance, requiring a few common tools or no tools at all.
Level 2: Maintenance that can be performed by the response team's maintenance shop, if adequately equipped and trained.
Level 3 : Specialized maintenance that can be performed only by the factory or an authorized repair person.
Each facility should adopt the above scheme and list which repairs fall into each category for each type of protective clothing and equipment. Many manufacturers will also indicate which repairs, if performed in the field, void the warranty of their products. All repairs made must be recorded on the records for the specific clothing along with appropriate inspection results.
RISKS
Heat Stress. Wearing full body chemical protective clothing puts the wearer at considerable risk of developing heat stress. This can result in health effects ranging from transient heat fatigue to serious illness or death. Heat stress is caused by a number of interacting factors, including:
Environmental conditions;
Type of protective ensemble worn
The work activity required; and
The individual characteristics of the responder.
When selecting chemical protective clothing and equipment, each item's benefit should be carefully evaluated for its potential for increasing the risk of heat stress. For example, if a lighter, less insulating suit can be worn without a sacrifice in protection, then it should be. Because the incidence of heat stress depends on a variety of factors, all workers wearing full body chemical protective ensembles should be monitored.
C. LEVEL OF PROTECTION.
LEVEL A:
Vapor protective suit (meets NFPA 1991) Pressure-demand, full-face SCBA Inner chemical-resistant gloves, chemical-resistant safety boots, two-way radio communication
OPTIONAL: Cooling system, outer gloves, hard hat
Protection Provided: Highest available level of respiratory, skin, and eye protection from solid, liquid and gaseous chemicals.
Used When: The chemical(s) have been identified and have high level of hazards to respiratory system, skin and eyes. Substances are present with known or suspected skin toxicity or carcinogenity. Operations must be conducted in confined or poorly ventilated areas.
Limitations: Protective clothing must resist permeation by the chemical or mixtures present. Ensemble items must allow integration without loss of performance.
LEVEL B:
Liquid splash-protective suit (meets NFPA 1992) Pressure-demand, full-facepiece SCBA
Inner chemical-resistant gloves, chemical-resistant safety boots, two-way radio communications
Hard hat.
OPTIONAL: Cooling system, outer gloves
Protection Provided: Provides same level of respiratory protection as Level A, but less skin protection. Liquid splash protection, but no protection against chemical vapors or gases.
Used When: The chemical(s) have been identified but do not require a high level of skin protection. Initial site surveys are required until higher levels of hazards are identified. The primary hazards associated with site entry are from liquid and not vapor contact.
Limitations: Protective clothing items must resist penetration by the chemicals or mixtures present. Ensemble items must allow integration without loss of performance.
LEVEL C:
Support Function Protective Garment (meets NFPA 1993) Full-facepiece, air-purifying, canister-equipped respirator Chemical resistant gloves and safety boots Two-way communications system, hard hat
OPTIONAL: Faceshield, escape SCBA
Protection Provided:. The same level of skin protection as Level B, but a lower level of respiratory protection. Liquid splash protection but no protection to chemical vapors or gases. >
Used When: Contact with site chemical(s) will not affect the skin. Air contaminants have been identified and concentrations measured. A canister is available which can remove the contaminant. The site and its hazards have been completely characterized.
Limitations: Protective clothing items must resist penetration by the chemical or mixtures present. Chemical airborne concentration must be less than IDLH levels. The atmosphere must contain at least 19.5% oxygen.
LEVEL D:
Coveralls, safety boots/shoes, safety glasses or chemical splash goggles
OPTIONAL: Gloves, escape SCBA, face-shield
Protection Provided: No respiratory protection, minimal skin protection.
Used When: The atmosphere contains no known hazard. Work functions preclude splashes, immersion, potential for inhalation, or direct contact with hazard chemicals.
Limitations: This level should not be worn in the Hot Zone. The atmosphere must contain at least 19.5% oxygen.
D.PROTECTIVE CLOTHING APPLICATIONS
1.Protective clothing must be worn whenever the wearer faces potential hazards arising from chemical exposure. Some examples include:
Emergency response;
Chemical manufacturing and process industries;
Hazardous waste site cleanup and disposal;
Asbestos removal and other particulate operations; and
Agricultural application of pesticides.
2.Within each application, there are several operations which require chemical protective clothing. For example, in emergency response, the following activities dictate chemical protective clothing use:
Site Survey: The initial investigation of a hazardous materials incident; these situations are usually characterized by a large degree of uncertainty and mandate the highest levels of protection.
Rescue: Entering a hazardous materials area for the purpose of removing an exposure victim; special considerations must be given to how the selected protective clothing may affect the ability of the wearer to carry out rescue and to the contamination of the victim.
Spill Mitigation: Entering a hazardous materials area to prevent a potential spill or to reduce the hazards from an existing spill (i.e., applying a chlorine kit on railroad tank car). Protective clothing must accommodate the required tasks without sacrificing adequate protection.
Emergency Monitoring: Outfitting personnel in protective clothing for the primary purpose of observing a hazardous materials incident without entry into the spill site. This may be applied to monitoring contract activity for spill cleanup.
Decontamination: Applying decontamination procedures to personnel or equipment leaving the site; in general a lower level of protective clothing is used by personnel involved in decontamination.
E.CLASSIFICATION OF PROTECTIVE CLOTHING.
1.Personal protective clothing includes the following:
Fully encapsulating suits;
Nonencapsulating suits;
Gloves, boots, and hoods;
Firefighter's protective clothing;
Proximity, or approach clothing;
Blast or fragmentation suits; and
Radiation-protective suits
Design.
Categorizing clothing by design is mainly a means for describing what areas of the body the clothing item is intended to protect.In emergency response, hazardous waste site cleanup, and dangerous chemical operations, the only acceptable types of protective clothing include fully or totally encapsulating suits and nonencapsulating or "splash" suits plus accessory clothing items such as chemically resistant gloves or boots. These descriptions apply to how the clothing is designed and not to its performance.
Performance.
Vapor-protective suits (NFPA Standard 1991) provide "gas-tight" integrity and are intended for response situations where no chemical contact is permissible.
Liquid splash-protective suits (NFPA Standard 1992) offer protection against liquid chemicals in the form of splashes, but not against continuous liquid contact or chemical vapors or gases.
Support function protective garments (NFPA Standard 1993) must also provide liquid splash protection but offer limited physical protection.
Service Life.
Clothing item service life is an end user decision depending on the costs and risks associated with clothing decontamination and reuse.
Protective clothing may be labeled as:
Reusable, for multiple wearings; or
Disposable, for one-time use.
The distinctions between these types of clothing are both vague and complicated. Disposable clothing is generally lightweight and inexpensive. Reusable clothing is often more rugged and costly. The basis of this classification really depends on the costs involved in purchasing, maintaining, and reusing protective clothing.
PROTECTIVE CLOTHING SELECTION FACTORS
F.CLOTHING DESIGN. Manufacturers sell clothing in a variety of styles and configurations.
1.Design Considerations.
Clothing configuration;
Components and options;
Sizes;
Ease of donning and doffing;
Clothing construction;
Accommodation of other selected ensemble equipment;
Comfort; and
Restriction of mobility.
G.MATERIAL CHEMICAL RESISTANCE. Ideally, the chosen material(s) must resist permeation, degradation, and penetration by the respective chemicals.
1.Permeation is the process by which a chemical dissolves in or moves through a material on a molecular basis.
Permeation breakthrough time is the most common result used to assess material chemical compatibility. The rate of permeation is a function of several factors such as chemical concentration, material thickness, humidity, temperature, and pressure. However, temperature and pressure effects may enhance permeation and reduce the magnitude of this safety factor.
2.Degradation involves physical changes in a material as the result of a chemical exposure, use, or ambient conditions (e.g. sunlight). The most common observations of material degradation are discoloration, swelling, loss of physical strength, or deterioration.
3.Penetration is the movement of chemicals through zippers, seams, or imperfections in a protective clothing material.
H.PHYSICAL PROPERTIES.
1.As with chemical resistance, manufacturer materials offer wide ranges of physical qualities in terms of strength, resistance to physical hazards, and operation in extreme environmental conditions. Comprehensive manufacturing standards such as the NFPA Standards set specific limits on these material properties, but only for limited applications, i.e. emergency response.
I.EASE OF DECONTAMINATION. The degree of difficulty in decontaminating protective clothing may dictate whether disposable or reusable clothing is used, or a combination of both.
J.COST. Protective clothing end users must endeavor to obtain the broadest protective equipment they can buy with available resources to meet their specific application.
K.CHEMICAL PROTECTIVE CLOTHING STANDARDS. Protective clothing buyers may wish to specify clothing that meets specific standards, such as 1910.120 or the NFPA standards. The NFPA Standards do not apply to all forms of protective clothing and applications.
GENERAL GUIDELINES
RECOMMENDED CHEMICALS TO EVALUATE THE PERFORMANCE OF PROTECTIVE CLOTHING MATERIALS
FIELD SELECTION OF CHEMICAL PROTECTIVE CLOTHING.
1.Testing material specimens using newly developed field test kits may offer one means for making an on-site clothing selection. A portable test kit has been developed by the EPA using a simple weight loss method that allows field qualification of protective clothing materials within one hour. Use of this kit may overcome the absence of data and provide additional criteria for clothing selection.
2.Selection of chemical protective clothing is a complex task and should be performed by personnel with both extensive training and experience.
Under all conditions, clothing should be selected by evaluating its performance characteristics against the requirements and limitations imposed by the application.
DECONTAMINATION PROCEDURES
DEFINITION AND TYPES
Decontamination is the process of removing or neutralizing contaminants that have accumulated on personnel and equipment. This process is critical to health and safety at hazardous material response sites. Decontamination protects end users from hazardous substances that may contaminate and eventually permeate the protective clothing, respiratory equipment, tools, vehicles, and other equipment used in the vicinity of the chemical hazard; it protects all plant or site personnel by minimizing the transfer of harmful materials into clean areas; it helps prevent mixing of incompatible chemicals; and it protects the community by preventing uncontrolled transportation of contaminants from the site.
There are two types of decontamination:
Gross decontamination: To allow end user to safely exit or doff the chemical protective clothing.
Decontamination for reuse of chemical protective clothing.
TYPES OF CONTAMINATION
i. Surface Contaminants. Surface contaminants may be easy to detect and remove.
ii. Permeated Contaminants. Contaminants that have permeated a material are difficult or impossible to detect and remove. If contaminants that have permeated a material are not removed by decontamination, they may continue to permeate the material where they can cause an unexpected exposure.
Four major factors affect the extent of permeation:
1. Contact time. The longer a contaminant is in contact with an object, the greater the probability and extent of permeation. For this reason, minimizing contact time is one of the most important objectives of a decontamination program.
2. Concentration. Molecules flow from areas of high concentration to areas of low concentration. As concentrations of chemicals increase, the potential for permeation of personal protective clothing increases.
3. Temperature. An increase in temperature generally increases the permeation rate of contaminants.
4. Physical state of chemicals. As a rule, gases, vapors, and low-viscosity liquids tend to permeate more readily than high-viscosity liquids or solids.
EVALUATION OF BARRIER PROPERTIES OF PROTECTIVE CLOTHING
The tests for assessing the performance characteristics of chemical protective clothing:
1. Degradation resistance
2. Penetration resistance
3. Permeation resistance
Degradation resistance test can only be used as a screening test which can show clear impossibility of using particular material for certain chemicals. Whereas; barrier properties of CPC can be determined by penetration and permeation resistance tests.
Degradation resistance
Degradation is defined as change in a materials physical properties as a result of chemical exposure. [physical properties may include weight of material, dimensions, tensile properties, thickness or any other characteristic.
Which may influence the performance of protective clothing when used in particular application. Dramatic degradation due to chemical exposure indicates the total incompatibility of the material with the chemical.
Penetration resistance
Penetration is defined as the floe of chemicals through closures, porous materials, seams and pinholes or any other imperfection in protective clothing. The penetration resistance tests is divided into two categories viz.
Run-off based tests and hydrostatic based tests.
Run-off based tests
These tests are characterized by contact of liquid chemicals with the materials by force of gravity over a specified distance. Usually specimen is supported at an angle of 45 degree allowing chemical to run-off, a large amount of water is delivered onto the specimen and the amount of water underneath the specimen is measured.
Index of penetration (P) = Mp/Mt * 100
Where: Mp= mass of the liquid deposited under the specimen
Mt= mass of test liquid discharged onto the test specimen
Hydrostatic based tests
It involves pressurization liquid behind or underneath the specimen. Water is used as challenge liquid. Water is introduced above the clamped specimen at a pressure controlled by water in rising column. A mirror is fixed below the specimen to allow the operator to view the underside of specimen for appearance of water droplets. The hydraulic pressure is increased until leakage occurs underneath the specimen.
Limitations of penetration resistance tests:
1.visual observations involved in the test leads to bias results.
2.liquid penetration in most cases occurs in the form of fine droplets which is difficult to be visualized.
3.water is used as a challenge liquid which has different nature than actual chemical.
Permeation resistance
Permeation is a process of chemical penetration into chemical protective clothing at molecular level. In this process, chemical is first absorbed on exposure side of material, then diffused through material and finally desorbs from the other surface. Resistance of the material to permeation is expressed in terms of break through time and permeation rate. Break through detection time is defined as the elapsed time measured from the start of the test to the sampling time that immediately proceeds the sampling time at which the test chemical is first detected. Break through time is an important consideration when choosing between CPC materials with similar degradation characteristics, while permeation rate is a measure of flux through a unit area of material for a unit time.
INSPECTION, STORAGE, AND MAINTENANCE
The end user in donning protective clothing and equipment must take all necessary steps to ensure that the protective ensemble will perform as expected. During emergencies is not the right time to discover discrepancies in the protective clothing. Teach end user care for his clothing and other protective equipment in the same manner as parachutists care for parachutes. Following a standard program for inspection, proper storage, and maintenance along with realizing protective clothing/equipment limitations is the best way to avoid chemical exposure during emergency response.
INSPECTION
An effective chemical protective clothing inspection program should feature five different inspections:
Inspection and operational testing of equipment received as new from the factory or distributor.
Inspection of equipment as it is selected for a particular chemical operation.
Inspection of equipment after use or training and prior to maintenance.
Periodic inspection of stored equipment.
Periodic inspection when a question arises concerning the appropriateness of selected equipment, or when problems with similar equipment are discovered.
Clothing/equipment item ID number;
Date of the inspection;
Person making the inspection;
Results of the inspection; and
Any unusual conditions noted.
Periodic review of these records can provide an indication of protective clothing which requires excessive maintenance and can also serve to identify clothing that is susceptible to failure.
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