HAZWOPER 40 -Lesson 13: Confined Spaces
Labeling and Posting
All warning signs shall be printed in English and also be printed in the predominant language of non-English reading employees. Employees unable to read labels and posted signs must receive additional information regarding hazardous areas and should be informed of the instructions printed on the signs. All entrances to confined space must be posted. Signs shall include but are not limited to the following information: emergency procedures, including phone numbers of EMS (emergency medical services), and response and rescue teams must be posted conspicuously within the immediate area of the confined space.
Ventilation
As stated earlier, one of the greatest hazards in confined spaces is the atmosphere. It can contain flammable gases, toxic gases, or an atmosphere depleted of or enriched in oxygen. Ventilation is needed when an IDLH (immediately dangerous to life and health), or nearly IDLH, atmosphere exists in confined spaces. IDLH means toxic gas levels are above OSHA's permissible exposure level, a flammable gas's concentration is greater than 10 percent of its lower explosive limit (LEL), or oxygen concentration is less than 19.5 percent or greater than 23.5 percent. Ventilation is not limited to those situations. Very hot environments can be ventilated with cooler air. Atmospheres that contain toxic gases can be ventilated even though the concentration is still below the PEL. Some sources say that ventilation is adequate when it exchanges the atmosphere in the space 30 times per hour with 12 changes made prior to entry.
Asphyxia
Asphyxia occurs when the body is deprived of oxygen for one reason or another. As we have seen, engulfment or oxygen-deficient atmospheres are probably the two most common causes of asphyxia. Usually the person is unconscious, cyanotic (blue in color), and not breathing. Obviously, initiation of mouth-to-mouth resuscitation and CPR (if the heart has stopped) is critical for the patient's survival. This must not be done while the patient is in the confined space.
Work Practices
Before entering a confined space, employees shall review the specific guidelines appropriate for safe entry and emergency exit. These guidelines or standards must be compiled by the qualified person and be definitive on all the possible hazards in areas covered by such guidelines.
Testing and Monitoring
Central to safe permit-space operations is atmospheric monitoring. From the assignment of protective gear to limitations of work practices, the results of this testing will govern almost every phase of entry. Also, in an implied way, OSHA requires atmospheric testing. There are three main atmospheric hazards that cause concern in confined spaces: Oxygen depletion Flammability Toxicity Our monitoring practices and instruments should be geared toward these three central hazards.
Heart Attack
Characterized usually by chest pain, shortness of breath, nausea, and weakness, heart attack is one of the greatest medical killers of industrial and municipal workers. Usually the onset of severe chest pain is fairly rapid but any chest pain should be cause for concern. Appropriate treatment includes immediate removal from the confined space, early activation of EMS (emergency medical services), rest, oxygen administration, and CPR if cardiac arrest occurs.
Burns
Confined space entrants can suffer everything from minor burns to massive burns caused by flash fire and explosion. Removal from the space and EMS activation are initial priorities. With minor burns, ointments or salves can be used, but they should NOT be applied to major burns. Major burns require medical attention and infection is the primary concern. The patient should be kept warm. The burns must be cleansed and dressed as soon as possible, but by a physician. Respiratory complications are common for confined space fire victims.
Entry Rescue
Entry rescue is clearly the form of rescue that presents the greatest risk to the rescuer. It entails actually placing an individual into the hazardous space. Entry rescues should be avoided whenever possible. If entry rescue cannot be avoided, then SCBA, lifelines, harnesses, retrieval systems, and appropriate levels of protective clothing are required.
Medical Issues
Everyone associated with confined space operations should have a basic understanding of the types of medical emergencies that they may encounter. To effectively do this, it is necessary to recognize the potential problems, be able to activate emergency medical services in your plant or municipality, and provide first aid prior to the arrival of medically trained personnel. OSHA recognizes the need for some level of medical awareness. It has mandated that all individuals associated with confined space entry and/or rescue be trained in CPR and basic first aid. At least one individual with current certification should be available during rescue operations. All individuals associated with confined space operations also need to know the location and operation of emergency medical supplies and equipment. It is the attendant's job to summon emergency medical assistance in the event of a medical problem. If an entrant has a serious medical problem the entire space should be evacuated immediately. Any medical affliction that occurs within the space should be assumed caused by a change in the confined space. If an injured entrant is exposed to a substance, the MSDS or other written information must be made available to the medical team treating the exposed entrant. Additional concerns with regard to medical issues include heart attack, asphyxia, chemical toxicity, heat stroke, burns, fractures, and lacerations. Though these considerations are important, extrication of the victim from the confined space should be implemented prior to the administration of basic first aid.
Other Hazards
In addition to cave-in hazards and secondary hazards related to cave-ins, there are other hazards from which workers must be protected during excavation-related work.
Lacerations
Lacerations give rise to three primary concerns: Blood loss Infection Possible exposure to contaminated blood by the rescuer In most instances blood loss from lacerations can look severe, but be in reality not so significant. Severe arterial bleeding, on the other hand, is life-threatening. By applying direct pressure, bleeding can usually be stopped. Obviously, initial treatment includes evacuation from the space and prompt EMS notification. A company nurse or physician should evaluate any employee for potential infection if he or she sustains a laceration in a confined space.
Learning Objectives At the completion of this lesson, you will be able to:
List OSHA guidelines for what should be documented on an entry permit. Name three main atmospheric hazards that cause concern in confined spaces. Discuss the two types of forced ventilation. Describe the two most common causes of asphyxia. Identify concerns associated with lacerations.
Negative-Pressure Ventilation
Negative-pressure ventilation is literally the reverse of positive-pressure ventilation in that the fan is turned around and the contaminated air is drawn out of the container. Again, ventilation is very inefficient, if there is only one ventilation opening. The ventilation method is dependent upon the equipment available. Most ventilation fans are not explosion proof. If the atmosphere to be removed from the container is flammable, the use of negative-pressure ventilation requires drawing the gas through the fan, which greatly increases the risk of ignition by the fan's power. Many high capacity fans get their power from an internal combustion engine. If such a fan were used to remove an oxygen-deficient atmosphere, the engine would perform poorly since the atmosphere used by the carburetor would be low in oxygen. Conversely, a run-away situation can result by drawing an oxygen-enriched (or oxidizer) or fuel-enriched atmosphere through the fan. Pneumatic powered fans are sometimes used because they do not present an ignition sources and can be very powerful when run with a large industrial compressor located remotely and attached with long air lines.
Other Medical Considerations
Preventative care for those individuals who enter confined spaces is highly recommended, especially screening physicals. Immunizations should be kept up to date. Any type of injury or hazardous material exposure should be documented and evaluated. Worker's compensation benefits, as well as effective medical care, depend on promptly filling out necessary forms and reports. Prevention of injury is the hallmark of the permit system. The permit safety measures, if taken seriously, will greatly reduce the chance for a confined space medical emergency.
Introduction
The possibility of the occurrence of confined spaces at hazardous waste sites should not be overlooked. Entering a confined space can be deadly. It is important to recognize confined spaces and to distinguish confined spaces from permit-required confined spaces. Employees must be made aware of the existence of confined spaces at hazardous waste sites. NOTE: All individuals involved in confined space entry are required to have appropriate levels of confined space entry training.
Three Types of Rescue
Three types of rescue can be employed in the confined space setting: Self-rescue Non-entry rescue (external) Entry rescue (internal)
Permit System
To ensure the safety of the individual entering the confined space, the permit system has been devised. In reality, the permit is a mandatory checklist of the precautionary measures that need to be taken before entry. It is mandatory that an employer implement a functional permit program if a permit-required confined space is on the premises. Before entry is authorized, the employer must document: Measures that have been implemented to prevent unauthorized entry. Hazards that have been identified and evaluated before employee entry. The means, procedures, and practices necessary for safe permit space entry operations and show these to have been developed and implemented. IMAGE: https://player.360training.com/ICPFileSystem/PersistentAssets/160953/281133/permit_system.pdf
Chemical Toxicity
A person who inhales a toxic chemical and suffers acute effects will probably have a shortness of breath as the primary symptom. This is especially true if the chemical is an irritant. Chemical asphyxiates usually cause cyanosis and absence of breathing. Regardless of the type of chemical inhaled, removal of the individual from the space is the first priority followed by EMS activation. CPR may be necessary if the victim's heart has stopped beating. Rescuers must be careful not to contaminate themselves with the toxic chemical by coming into unprotected contact with the patient. If the chemical was absorbed, removal of clothing and decontamination are necessary.
Permit-Required Confined Space Entry
As the name implies, a work permit is required prior to entering a permit space. Common types of spaces that would require permits include storage tanks, process vessels, silos, vaults, storage bins, hoppers, ship compartments, exhaust ducts, sewers, tunnels, and boilers. A space does not have to be enclosed to be considered a permit-required confined space. Pits, trenches, and open-topped vats also fit the OSHA description since they may have limited means of entry and exit, and are not intended for habitation, and could possess hazardous atmospheres. OSHA has determined that individuals who enter permit-required confined spaces are at a significant risk of death or injury. Therefore, all permit-required confined spaces are to be considered dangerous until proven otherwise
Hazardous Atmospheres
Before an employee is allowed to enter an excavation, a competent person must test if it is over four feet deep or if oxygen deficiency or a hazardous atmosphere exists or could reasonably be expected to exist. If hazardous conditions exist, controls such as proper respiratory protection or ventilation must be provided. Also, controls used to reduce atmospheric contaminants to acceptable levels must be tested regularly.
Preliminary Information to Gather
Before any excavation actually begins, the Standard requires the employer to determine the estimated location of utility installations such as sewer, telephone, fuel, electric, waterlines, or any other underground installations that can be encountered while digging. Also, before starting, the contractor must contact utility companies or involved property owners and inform them, within their established or customary local response times. The contractor must also ask the utility companies (or owners) to identify the exact location of all underground installations. If the utility cannot respond within 24 hours (unless the period required by state or local law is longer), or if they cannot find the exact location of the utility installations, the contractor may proceed with caution. To find the exact location of underground installations, workers must use safe and acceptable means. If underground installations are exposed, OSHA also requires that they be removed, protected, or properly supported. When all the necessary specific information about the job site is assembled, the contractor is ready to determine the amount, kind, and cost of the safety equipment needed. A careful inventory of the safety items on hand should be made before deciding what additional safety material must be acquired. No matter how many trenching, shoring, and back-filling jobs have been done in the past, each job should be approached with the utmost care and preparation.
Prior to Entering a Confined Space
Before entering a confined space, a review of the specific guidelines for appropriate safe entry and emergency exit is vital. Actual entry into a confined space should only be allowed after the following has taken place: All entrants and attendants have received proper training and equipment. The designated authority on-site has issued the proper permit. The appropriate PPE is in place and utilized. OSHA's required procedures have been put into effect, especially the "buddy system. The procedures set forth in the following sections are based on OSHA Standard in 29 CFR 1910.146. They are a means of protecting worker health and of avoiding accidental injury and death associated with entering, working in, and exiting confined spaces. They are designed to make the confined space safe, to make workers aware of related hazards, and to train in safe work practices. A preliminary evaluation of the site's characteristics must be performed prior to site entry. A secondary more detailed evaluation must be conducted to further identify existing hazards to aid in the selection of appropriate engineering controls and personal protective equipment (PPE) for future site activities. The evaluation must include all suspected conditions that are immediately dangerous to life or health (IDLH) or that may cause serious harm to employees (e.g., confined space entry, potentially explosive or flammable situations, visible vapor clouds, etc.).
Confined Space Rescue
Confined space emergencies are among the leading causes of multiple deaths in the workplace. In most cases, an emergency begins with one or two people succumbing to a confined space hazardous exposure. Then, untrained and/or unprotected rescuers add to the problem by entering the space and becoming victims themselves. In fact, about 60 percent of victims are would-be rescuers. Additionally, a majority of these individuals are supervisors and/or senior personnel who should know better. Oddly enough there are cases where the initial entrants survive and the would-be rescuers die. With this in mind, it appears that the greatest single piece of advice to be passed along is to "resist the overwhelming temptation to try to save a colleague by entering the space unprotected."
Cave-ins and Protective Support Systems
Excavation workers are exposed to many hazards, but the chief hazard is the danger of cave-ins. OSHA requires that in all excavations, employees exposed to potential cave-ins must be protected by the following: Sloping or benching (i.e., terracing/stepping) Shielding Shoring/bracing Designing a protective system can be complex because of the number of factors involved; for example, soil classification, depth of cut, water content of soil, changes due to weather and climate, or other operations in the vicinity.
Fractures
Fractures are common injuries in confined spaces. Fractures should be immobilized if conditions within the space permit. If not, evacuation of the patient from the space should proceed as carefully as possible. A patient who has a fracture because of a fall should also be evaluated for other more serious internal injuries. In most cases, fractures of the extremities do not present a life-threatening situation.
Self-Rescue
In self-rescue, an entrant recognizes a hazardous exposure and is able to exit from the space with no assistance. Many times self-rescue results because an entrant feels ill. In this situation, the assumption is that a hazard within the space is causing the problem and that evacuation is necessary until the problem is identified. Obviously, self-rescue has many advantages over the other two forms of rescue. With self-rescue, emergency rescue personnel do not have to enter the space. Risky extrication and/or removal techniques are not required if self-rescue can be done. Also, by virtue of the fact that the individual is still conscious, the chances that the entrant will recover from the emergency are good. Hazard recognition can prevent serious exposure and injury.
The Employer's Safety and Health Program
It is important for the contractor to establish and maintain a safety and health program for the work site. The program should provide adequate policies, procedures, and practices to protect employees from, and enable them to recognize job-related safety and health hazards. An effective program includes provisions for the systematic identification, evaluation, and prevention or control of workplace hazards. The contractor must identify potential hazards that can arise from foreseeable conditions, both generally within the site and specific to certain tasks. The program can be written or verbal, but it should reflect the unique characteristics of the job site. Employers must provide any workers who are exposed to public vehicular traffic with warning vests or other suitable garments. The garments must be well marked, contain reflectors, or be made with high-visibility material. The employer is responsible to ensure that workers wear their protective equipment. Workers must also be instructed to remove any surface obstacles that can create a hazard at the worksite. No employee should operate a piece of equipment without being properly trained to handle it and fully alerted to its potential hazards. In the training as well as the site safety and health program, it is also important to incorporate procedures for fast notification and investigation of accidents.
Planning for Safety
Many on-the-job accidents are a direct result of inadequate planning. Correcting shoring or sloping mistakes after work has begun slows down the operation, adds to the cost, and increases the possibility of an excavation failure. The contractor should build safety into pre-bid planning in the same way all other pre-bid factors are considered. It is a good idea for contractors to develop a safety checklists before preparing a bid, to make certain that information about the job site is adequate and that all needed items will be made available. Contractors should also make sure that they have enough space to safely dig their excavations in relation to property lines, neighboring utilities, adjacent structures, etc and as the project scope changes these considerations must be taken into account and budgeted for. In general, the deeper the excavation the wider it needs to be and the more spoils will be generated. Othwerwise shoring systems likely need to be employed which takes additional planning and expense. These checklists should incorporate elements of relevant standards as well as other information necessary for safe operations. Before preparing a bid, the following specific site conditions should be taken into account: Traffic Nearness of structures and their conditions Soil Surface and ground water The water table Overhead and underground utilities Weather More About: These and other conditions can be determined by job site studies, observations, test borings for soil type or conditions, and consultations with local officials and utility companies.
Non-Entry Rescue
Non-entry rescue, as the name implies, is rescue performed from outside the space. Prior to entry, retrieval/lifelines (further discussed in "Retrieval Lines" below) and body harnesses should be in place in the event that conditions change. In most cases, non-entry rescue involves removal using these lines. It is important to plan and conduct the entry with this form of rescue in mind. Pulley systems, tripods, and space entry ways should be arranged so that there is little chance that lines can tangle. Non-entry rescue cannot be used for an individual who is entangled, trapped, or bound-up within the space. It can be used for engulfment (i.e., burying) situations as long as the amount of engulfing material is small enough to allow the victim to be unearthed using line tension.
Outside Rescue Services
OSHA is aware that, from the viewpoint of elapsed time, in-plant rescue services are preferred. OSHA also realizes that not all employers have the equipment and/or the personnel for such a team. If an outside rescue service is to be used, the employer must evaluate the following before a rescue becomes necessary: The rescue service's response time Its continuous availability during the entry Its rescue capabilities
Scope and Application
OSHA's revised rule applies to all open excavations made in the earth's surface, which includes trenches. According to the OSHA Construction Health and Safety Standard, a trench is referred to as a narrow excavation made below the surface of the ground in which the depth is greater than the width, the width not exceeding 15 feet. An excavation is any human made cut, cavity, trench, or depression in the earth's surface formed by earth removal. This can include excavations for anything from cellars to highways.
Lesson Focus This lesson focuses on the following topics:
Part 1: Procedures and Responsibilities Prior to Entering a Confined Space Permit-Required Confined Space Entry Personnel Responsibilities in a Confined Space Work Area Part 2: Protective Measures Ventilation Safety Equipment and Clothing Confined Space Rescue Medical Issues Part 3: Excavations Excavation Planning for Safety The Employer's Safety and Health Program Cave-ins and Protective Support Systems Safety Precautions Installation and Removal of Protective Systems
On-Site Rescue Teams
Personnel assigned to an in-plant rescue team must be provided with, and trained in the proper use of, the personal protective equipment necessary for making rescues from the employer's permit spaces. The employer must ensure that the on-site rescue team is trained to perform the assigned rescue functions and to be authorized confined space entrants. Rescue teams are required to practice making permit-space rescues at least once every twelve months by means of simulated rescue operations. In these simulated rescue operations, rescuers remove dummies, mannequins, or personnel through representative openings and portals. The size, configuration, and accessibility of these openings should closely resemble those of the permit spaces from which rescues may be required.
Personnel Responsibilities in a Confined Space Work Area
Personnel who work in the vicinity of confined spaces must be aware of the associated hazards. Personnel who are required to work in a confined space or in support of those working in a confined space have additional responsibilities in the following areas: Planning entry and exit procedures Rescue and training drills at intervals as determined necessary by the employer Use of testing equipment for atmospheric monitoring Lockout procedures Ventilation Duties of attendant and entrant Safety equipment use
Safety Equipment and Clothing
Recall that the purpose of chemical protective clothing (CPC) and personal protective equipment (PPE) is to shield or isolate individuals from the chemical, physical, and biological hazards that may be encountered. Careful selection and use of adequate PPE for confined space entry should protect the lungs, skin, eyes, ears, nose, face, hands, feet, head, body, etc. Of course engineering and administrative controls should be employed before relying on PPE. No single combination of protective equipment and clothing is capable of protecting against all hazards. Therefore, PPE should be used in conjunction with other protective methods. The use of PPE can itself create significant worker hazards, such as heat stress, physical and psychological stress, and impaired vision, mobility, and communication. In general, the greater the level of PPE protection, the greater the associated risks. For any given situation, equipment and clothing should be selected that provide an adequate level of protection. Overprotection, as well as under protection, can be hazardous and should be avoided.
Excavation
The Occupational Safety and Health Administration (OSHA) issued its first Excavation and Trenching Standard in 1971 to protect workers from excavation hazards. Since then, OSHA has amended the Standard several times to increase worker protection and to reduce the frequency and severity of excavation accidents and injuries. Despite these efforts, excavation-related accidents resulting in injuries and fatalities continue to occur. To better assist excavation firms and contractors, OSHA has completely updated the existing Standard to simplify many existing provisions by: Adding and clarifying definitions Eliminating duplicate provisions and ambiguous language Giving employers added flexibility in providing protection for employees The Standard became effective March 5, 1990, and contains several new appendices. One appendix provides a consistent method of soil classification. Others provide sloping and benching requirements, pictorial examples of shoring tables, and selection charts that provide graphic summaries of requirements.
Trenches
The Standard permits excavation of two feet or less below the bottom of the members of a support or shield system if the system is designed to resist the forces calculated for the full depth, and there are no indications, while the trench is open, of a possible cave-in below the support system bottom. Also, the installation of support systems must be closely coordinated with the excavation of trenches. As soon as work is completed, the excavation should be back-filled as the protective system is dismantled. After the excavation has been cleared, workers should slowly remove the protective system from the bottom up, taking care to release members slowly.
Water Accumulation
The Standard prohibits employees from working in excavations where water has accumulated or is accumulating, unless adequate protection has been taken. If water removal equipment is used to control or prevent water accumulation, a competent person must monitor the equipment and operations to ensure proper usage. When water infiltrates an excavation the soil needs to be reclassified. OSHA also requires that diversion ditches, dikes, or other suitable means be used to prevent surface water from entering an excavation. Adequate drainage of the area adjacent to the excavation is necessary. Also, a competent person must inspect excavations subject to heavy rain runoff.
Safety Precautions
The Standard requires employers to provide support systems such as shoring, bracing, or underpinning to ensure the stability of adjacent structures such as buildings, walls, sidewalks, or pavement. The Standard prohibits excavation below the level of the base or footing of any foundation or retaining wall unless: A support system such as underpinning is provided. The excavation is in stable rock. A registered professional engineer determines that the structure is sufficiently removed from the excavation and that the excavation will not pose a hazard to employees. Excavations under sidewalks and pavement are also prohibited unless an appropriately designed support system is provided or another effective method is used.
On-the-Job Evaluation
The Standard requires that a competent person inspect, on a daily basis, excavations and the adjacent areas for possible cave-ins, failures of protective systems and equipment, hazardous atmospheres, or other hazardous conditions. If these conditions are encountered, then exposed employees must be removed from the hazardous area until the necessary safety precautions have been taken. Inspections are also required after natural (e.g., heavy rains) or human-caused events (e.g., blasting), which can increase the potential for hazards. Larger and more complex operations should have a full-time safety official who makes recommendations to improve the implementation of the safety plan. In a smaller operation, the safety official can be part-time and will usually be a supervisor. Supervisors are the contractor's representatives on the job. Supervisors should conduct inspections, investigate accidents, and anticipate hazards. They should ensure that employees receive on-the-job safety and health training. They should also review and strengthen overall safety and health precautions to guard against potential hazards, get the necessary worker cooperation in safety matters, and make frequent reports to the contractor. Managers and supervisors must set a safety example. It is essential that when visiting the job site, all managers, regardless of status, wear the prescribed personal protective equipment such as safety shoes and glasses, hardhats, and other necessary gear (see CFR 1926.100 and 102). Employees must also take an active role in job safety. After the contractor and supervisor have made certain that employees have been properly trained, workers should be responsible enough to wear and use PPE properly and follow safe work practices
Installation and Removal of Protective Systems
The Standard requires the following considerations for the protection of employees when installing support systems: Securely connect members of support systems. Safely install support systems. Never overload members of support systems. Install other structural members to carry loads imposed on the support system when temporary removal of individual members is necessary.
Atmosphere
The atmosphere in a confined space can be altered in many ways. In some cases, chemical treatment changes the atmosphere. This usually is done in industrial vessels where entry is frequent. In other cases, flammable vapors in the atmosphere can be absorbed using activated carbon. The most frequently used method of altering or replacing the atmosphere is through ventilation. Specific ventilation techniques vary according to: Size and orientation of the space Size of the exhaust opening Types of vapors to be removed Source of the replacement air Regardless of the ventilation technique used, it replaces a contaminated atmosphere with one that is uncontaminated.
Materials and Equipment
The employer is responsible for the safe condition of materials and equipment used for protective systems at excavations. Defective and damaged materials and equipment can result in the failure of a protective system and cause excavation hazards. To avoid possible failure of a protective system, the employer must ensure that: Materials and equipment are free from damage or defects. Manufactured materials and equipment are used and maintained in a manner consistent with the recommendations of the manufacturer and in a way that will prevent employee exposure to hazards. While in operation, damaged materials and equipment are examined by a competent person to determine if they are suitable for continued use. More About: If materials and equipment are not safe for use, they must be removed from service. These materials cannot be returned to service without the evaluation and approval of a registered professional engineer.
Access and Egress
The employer must provide safe access to and egress from all excavations. According to the OSHA regulations, when employees are required to be in trench excavations four feet deep or deeper, adequate means of exit, such as ladders, steps, ramps, or other safe means of egress must be provided and be within 25 feet of lateral travel. If structural ramps are used as a means of access or egress, a competent person qualified in structural design must plan them. Also, structural members used for ramps or runways must be uniform in thickness and joined in a manner that prevents tripping or displacement.
Isolation/Lockout/Tagout
The isolation procedures are specific for each type of confined space. Safety equipment required during this procedure is designated by the qualified person and is dependent upon the potential hazards involved. Permit-required confined spaces must be completely isolated from all other systems by physical disconnection, double block and bleed, or blanking off all lines. In continuous systems, where complete isolation is not possible, such as sewers or utility tunnels, specific written safety procedures approved and enforced by the employer are used.
Ventilation
The type of ventilation is dependent upon two principles: The effect of the contaminant's vapor density Application of positive or negative pressure Example Suppose we had a vertical tank filled with methane gas. If we opened the hatch at the top, the methane would be vented out, because its vapor density is much lighter than the vapor density of air. If there were just one opening at the top, both the intake and exhaust gases would have to pass through the same opening. Though quite inefficient, the atmospheric changeover would occur in time. The process could be made much more efficient if a second opening were made at the bottom. As the methane would vent out the top, air would be drawn in through the bottom resulting in a more rapid atmospheric turnover. The greater the difference in vapor density, the faster natural ventilation will take place. Naturally, the reverse flow would occur if the atmosphere in the container had a vapor density greater than one, the vapor density of air. Many of the gases that need to be ventilated are either present in fairly low concentrations or have vapor densities close to one.
Falls and Equipment
These hazards include exposure to falls, falling loads, and mobile equipment. To protect employees from these hazards, employers must take the following precautions: Keep materials or equipment that might fall or roll into an excavation at least two feet from the edge of excavations, or have retaining devices, or both. Prohibit employees from working on faces of sloped or benched excavations at levels above other employees, unless employees at lower levels are adequately protected from the hazard of falling, rolling, or sliding material or equipment. Prohibit employees from going beneath loads that are handled by lifting or digging equipment.
Lesson Description
This lesson, Confined Spaces, focuses on OSHA Standard 29 CFR 1910.146, which regulates what the employer must do to make confined space entry work safe for workers. This lesson addresses both the employer's and the employee's confined space responsibilities. It reviews the types of hazards (i.e., soil, atmosphere, and gas) that must be identified and controlled. Specific details are provided pertaining to the use of proper engineering controls like positive- and negative-pressure ventilation systems, as well as the selection and use of PPE (such as appropriate respirators and body harness systems). Among the many issues addressed, the discussion of pre-entry training, rescue team responsibilities, and ensuring that all permit procedures are followed is of primary importance.
Forced Ventilation
This means that natural ventilation is not very effective. In the confined space entry context, natural ventilation does not usually proceed fast enough; therefore, forced ventilation must be employed. Most commonly, forced ventilation involves a fan, air compressor, or other machine. There are two types of forced ventilation: Positive-pressure ventilation Negative-pressure ventilation Natural wind can also positively or negatively ventilate a container. The effectiveness of natural ventilation depends on: The number of openings The opening sizes The orientation of the openings to the wind Wind speed and consistency
Avoid Risk
Trenching and excavation work presents serious risks to all workers involved. The greatest risk, and one of primary concern, is that of a cave-in. Furthermore, when cave-in accidents occur, they are much more likely to result in worker fatalities than other excavation-related accidents. Strict compliance, however, with all sections of the Standard will prevent and/or greatly reduce the risk of cave-ins as well as other excavation-related accidents.
Entry Permit OSHA Guidelines
Usually a company or municipality will develop its own format for the permit. OSHA provides the following guidelines on what needs to be documented on an entry permit: The permit space to be entered The purpose of the entry The date and the authorized duration of the entry permit The authorized entrants by name, or by a means that will allow the attendant to determine quickly and accurately which authorized attendants are within the space The personnel, by name, serving as attendants The individual, by name, serving as entry supervisor, with a space for the signature or initials of the entry supervisor who originally authorized entry More About: One must understand the inter-relationship between emergency response plan, medical surveillance requirements, confined space entry procedures, spill containment program, and any appropriate work practices. IMAGE: https://player.360training.com/ICPFileSystem/PersistentAssets/160948/281125/Confined_Permit.pdf The individual, who authorizes the entry, must sign the permit. This identifies the party responsible should any problem arise during entry. It is assumed that the affixing of one's signature to the permit will insure that the permit process has been taken seriously and that all protective measures are actually in place. Permits have a definite duration of effect and are canceled when the entry is over. This will assure that all entrants and their equipment have exited the space before the space is returned to its normal state. A permit is also canceled when an emergency develops and/or an evacuation of the space is necessitated. The entry permit is kept for one year. Employers must perform a review of the permit-required confined space program within one year after each entry or do an annual review covering all entries during a 12-month period. After the review, the program should be revised, as necessary, to ensure safety. If no entries are performed during a 12-month period, then no review of the program is required.
Positive-Pressure Ventilation
When a space is ventilated by positive pressure, air is blown into the space, thus pressurizing it. The increased pressure forces the contaminated atmosphere out and allows uncontaminated atmosphere in. The scouring action of positive-pressure ventilation also helps to eliminate dead spots where contamination levels can still be high. In many cases, tubes are attached to the output side of the fan, channeling the air to where it is needed. This is very helpful when the airstream needs to bend, as in manhole ventilation, or when only one opening exists in the container. Otherwise, the turbulence caused between inflow and outflow inhibits exchange. By keeping the inflow and outflow gases separate, turbulence is essentially eliminated and efficiency is greatly increased.