Methods to Lower Workplace PELs

According to OSHA policy, engineering controls and work practices are preferred over personal protective equipment to control employee exposures to airborne contaminants.

Engineering controls involve the use of a local exhaust ventilation, general ventilation, isolation of the worker and enclosure of the source of emissions, process modifications, equipment modifications, and substitution of nonhazardous or less hazardous chemicals. These methods may be used alone or in combination, depending upon the industrial processes involved. These controls are widely used and will effectively control exposures either by themselves, or coupled with changes in work practices.

Ventilation

Perhaps the most widely used technique for controlling chemical exposure is the use of ventilation. General ventilation uses the movement of air within the general work space to displace or dilute the contaminant with fresh outside air. General ventilation may not be the preferred control method, however, due to the large volumes of air movement required. Local exhaust ventilation uses a much smaller volume of air and controls emissions at the point or source from which contaminants are generated.

Isolation

Isolation involves placing a physical barrier between the hazardous operation and the worker. Many modern, automated manufacturing processes are now fully enclosed in ventilated cabinets. The effectiveness of such a control technique depends on the frequency with which the workers have to enter the enclosure during normal operations.

In other situations, the worker, rather than the process or machine, can be placed in an enclosure having a controlled atmosphere. Many processes which involve potential chemical exposures are operated remotely by operators from air conditioned booths isolated from the hazardous materials.

Substitution

Substitution refers to the replacement of a toxic chemical in a particular process or work area with another, less toxic or non-toxic product. Properly applied, substitution can be a very effective control technique. However, care must be taken to ensure that the proposed substitute performs in a similar manner to the product being replaced. In addition, it is essential that the substitute be carefully evaluated to ensure that in controlling one hazard, another different hazard is not inadvertently introduced. The substitute must also be compatible with existing manufacturing equipment and processes.

The success of these engineering control techniques will depend on the physical properties of the chemicals and emissions encountered (boiling point, vapor pressure, etc.) and the process operating conditions. In some cases, particularly with cleaning solvents, substitution may provide the quickest and most effective means of reducing exposure. In other situations, a major effort may be required to alter processes or install or expand local or general dilution ventilation.

OSHA has found that engineering controls and improved work practices are available to reduce exposure levels to the new levels in almost all circumstances. However, in some circumstances, respiratory protection may be necessary to complement engineering controls. Respiratory protection may be necessary to achieve compliance in some specific operations in some industries.

Engineering Controls vs. Protective Equipment

So in other words, the most desirable way to deal with an air contaminant is to alter the process so that the contaminant is no longer produced. If the process cannot be changed or materials substituted, a well designed ventilation system may be the best solution to the problem. If ventilation would require too large a volume of air to reduce the concentration of the contaminant, then respiratory protection may be a necessary short-term solution.

Pitfalls of Exposure Limits

Even though you have checked the PELs and the TLVs for your chemicals, brought the exposure numbers into the acceptable range, your workers may still be endangered. How could this be?

There are over 600,000 chemicals in use today. Information available for selecting an exposure limit is very scant. Only a small percentage of chemicals is even evaluated. Therefore, supporting data can be weak. Exposure limits are changed when new information becomes available. What is considered “safe” today, may be viewed in a different light tomorrow.

Individual sensitivity is a factor. Even at an acceptable exposure level, a given chemical may have a negative effect on certain people. So even if the exposure limit protects most people, it can not be relied upon to protect everyone.

Synergistic effects should be considered. Single substances are assigned individual ratings. Seldom in the real world is only one chemical in use at a time. What happens when several chemicals combine to produce effects far more harmful than those of any one substance?

Methods of Compliance | Asbestos

Q.	What are the three basic controls required initially in ALL operations covered in the Construction standard?
A.	Regardless of the exposure levels the controls required are: use of HEPA filtered vacuums when the source of the dust/debris is damaged ACM or disturbance of ACM or PACM; use of wet methods to control asbestos fiber dispersion; and prompt disposal of asbestos contaminated waste materials. These provisions apply to, for example, employers who install asbestos-containing material (no Class designation), clean up asbestos-containing debris at a construction site (Class IV), repair a boiler covered with asbestos-containing TSI (Class I or III), and remove asbestos-containing surfacing material (Class I). Certain roofing operations, however, are not subject to these requirements.
Q.	When does OSHA consider the use of wet methods infeasible?
A.	An employer can demonstrate infeasibility if he/she can show that wet methods cannot be used due to conditions such as electrical hazards, hot surfaces, and the presence of technical equipment which cannot tolerate moisture.
Q.	What is required for the disposal of asbestos-contaminated waste?
A.	All asbestos-contaminated waste must be promptly disposed of in leak-tight containers.
Q.	What is meant by the term "air sweeping"?
A.	Where the exposure is expected to be above the PELs, OSHA requires ventilation that moves contaminated air away from employees toward a HEPA filtered exhaust device. It does NOT mean that a general building ventilation system to vent asbestos contaminated air, would be acceptable under the standard.
Q.	Is the negative pressure enclosure the only effective system for larger removal operations?
A.	Negative pressure enclosure systems are effective in many circumstances in protecting workers both within and outside the enclosure. Other systems such as glove bags and mini-enclosures can be equally effective.
Q.	What is the major difference between the negative pressure enclosure and negative air ventilation?
A.	The negative pressure enclosure system is primarily designed to keep asbestos from contaminating the building. The air pressure inside the enclosure is less than outside the enclosure. Negative air ventilation draws clean air from outside the enclosure at sufficient quantities and at strategic locations, so as to provide clean air in the worker's breathing zone and is part of the negative enclosure system.
Q.	If an employer has a variety of work activities, how does one decide which class to follow?
A.	The classes are exclusive. For example, the stripping of 50 linear feet of thermal system insulation, whether or not it has been positively identified as asbestos containing material, is Class I, for it is the removal of PACM. Repair of a valve covered by ACM is Class III, since "removal" is not taking place, if less than one glove bag of ACM has been disturbed. Removal of flooring material containing ACM is Class II. If more than one "class" of work occurs simultaneously, the work must be performed according to the highest hazard classification.
Q.	Is all asbestos activity designated by "class"?
A.	All asbestos work under the Construction and Shipyard standards is not in the "class system." The installation of new asbestos-containing products does not carry a class designation, and thus the class-specific requirements do not apply to that activity. For work that does not readily fall into one of the four classes, the employer must comply with the PEL. Work covered by the General Industry standard is not included in the "class system."

Q.	Is misting considered a "wet method"?
A.	Wet methods encompass a range of work practices. For example, when removing material which is bound in a matrix, misting may be appropriate. Removing ACM or PACM which is not so bound, or where deterioration of the ACM has occurred, would require more aggressive wetting.

Methods to Lower Workplace PELs | Air Contaminants

According to OSHA policy, engineering controls and work practices are preferred over personal protective equipment to control employee exposures to airborne contaminants.

Engineering controls involve the use of a local exhaust ventilation, general ventilation, isolation of the worker and enclosure of the source of emissions, process modifications, equipment modifications, and substitution of nonhazardous or less hazardous chemicals. These methods may be used alone or in combination, depending upon the industrial processes involved. These controls are widely used and will effectively control exposures either by themselves, or coupled with changes in work practices.

Ventilation

Perhaps the most widely used technique for controlling chemical exposure is the use of ventilation. General ventilation uses the movement of air within the general work space to displace or dilute the contaminant with fresh outside air. General ventilation may not be the preferred control method, however, due to the large volumes of air movement required. Local exhaust ventilation uses a much smaller volume of air and controls emissions at the point or source from which contaminants are generated.

Isolation

Isolation involves placing a physical barrier between the hazardous operation and the worker. Many modern, automated manufacturing processes are now fully enclosed in ventilated cabinets. The effectiveness of such a control technique depends on the frequency with which the workers have to enter the enclosure during normal operations.

In other situations, the worker, rather than the process or machine, can be placed in an enclosure having a controlled atmosphere. Many processes which involve potential chemical exposures are operated remotely by operators from air conditioned booths isolated from the hazardous materials.

Substitution

Substitution refers to the replacement of a toxic chemical in a particular process or work area with another, less toxic or non-toxic product. Properly applied, substitution can be a very effective control technique.

However, care must be taken to ensure that the proposed substitute performs in a similar manner to the product being replaced. In addition, it is essential that the substitute be carefully evaluated to ensure that in controlling one hazard, another different hazard is not inadvertently introduced. The substitute must also be compatible with existing manufacturing equipment and processes.

The success of these engineering control techniques will depend on the physical properties of the chemicals and emissions encountered (boiling point, vapor pressure, etc.) and the process operating conditions. In some cases, particularly with cleaning solvents, substitution may provide the quickest and most effective means of reducing exposure. In other situations, a major effort may be required to alter processes or install or expand local or general dilution ventilation.

OSHA has found that engineering controls and improved work practices are available to reduce exposure levels to the new levels in almost all circumstances. However, in some circumstances, respiratory protection may be necessary to complement engineering controls. Respiratory protection may be necessary to achieve compliance in some specific operations in some industries.

Engineering controls vs. protective equipment

So in other words, the most desirable way to deal with an air contaminant is to alter the process so that the contaminant is no longer produced. If the process cannot be changed or materials substituted, a well designed ventilation system may be the best solution to the problem. If ventilation would require too large a volume of air to reduce the concentration of the contaminant, then respiratory protection may be a necessary short-term solution.

Methods of Control | Bloodborne Pathogens

Q. What is meant by the term universal precautions?

A. Universal Precautions is OSHAs required method of control to protect employees from exposure to all human blood and OPIM. The term, “Universal Precautions,” refers to a concept of bloodborne disease control which requires that all human blood and certain human body fluids are treated as if known to be infectious for HIV, HBV, and other bloodborne pathogens.

Q. What are engineering controls?

A. The term, “engineering controls,” refers to controls (e.g., sharps disposal containers, self-sheathing needles, safer medical devices, such as sharps with engineered sharps injury protections and needleless systems) that isolate or remove the bloodborne pathogens hazards from the workplace.

Q. Can employees of an ambulance medical rescue service eat or drink inside the cab of the unit?

A. Employees are allowed to eat and drink in an ambulance cab only if the employer has implemented procedures to permit employees to wash up and change contaminated clothing prior to entering the ambulance cab, has prohibited the consumption, handling, storage, and transport of food and drink in the rear of the vehicle, and has procedures to ensure that patients and contaminated materials remain behind the separating partition.

Q. What alternatives are acceptable if soap and running water are not available for handwashing?

A. Antispetic hand cleaner in conjunction with clean cloth/paper towels or antiseptic towelettes are examples of acceptable alternatives to running water. However, when these types of alternatives are used, employees must wash their hands (or other affected areas) with soap and running water as soon as feasible. This alternative would only be acceptable at worksites where soap and running water are not feasible.