This mandatory appendix contains the medical questionnaires that must
be administered to all employees who are exposed to asbestos, tremolite,
anthophyllite, and actinolite, or a combination of these minerals above
the permissible exposure limit (0.1 f/cc), and who will therefore be included
in their employer's medical surveillance program. Part 1 of the appendix
contains the initial medical questionnaire, which must be obtained for
all new hires who will be covered by the medical surveillance requirements.
Part 2 includes the abbreviated periodical medical questionnaire, which
must be administered to all employees who are provided periodic medical
examinations under the medical surveillance provisions of the standard.
WAC 296-62-07743
Appendix E--Interpretation and classification of chest roentgenograms--Mandatory.
(1) Chest roentgenograms shall be interpreted and classified in accordance
with a professionally accepted classification system and recorded on an
interpretation form following the format of the CDC/NIOSH (M) 2.8 form.
As a minimum, the content within the bold lines of this form (items one
through four) shall be included. This form is not to be submitted to NIOSH.
(2) Roentgenograms shall be interpreted and classified only by a B-reader,
a board eligible/certified radiologist, or an experienced physician with
known expertise in pneumoconioses.
(3) All interpreters, whenever interpreting chest roentgenograms made
under this section, shall have immediately available for reference a complete
set of the ILO-U/C International Classification of Radiographs for Pneumoconioses,
1980.
WAC 296-62-07745
Appendix F--Work practices and engineering controls for automotive brake
and clutch inspection, disassembly, repair and assembly--Mandatory.
This mandatory appendix specifies engineering controls and work practices
that must be implemented by the employer during automotive brake and clutch
inspection, disassembly, repair, and assembly operations. Proper use of
these engineering controls and work practices will reduce employees' asbestos
exposure below the permissible exposure level during clutch and brake
inspection, disassembly, repair, and assembly operations. The employer
shall institute engineering controls and work practices using either the
method set forth in (1) or (2) of this appendix, or any other method which
the employer can demonstrate to be equivalent in terms of reducing employee
exposure to asbestos as defined and which meets the requirements described
in (3) of this appendix, for those facilities in which no more than 5
pairs of brakes or 5 clutches are inspected, disassembled, reassembled
and/or repaired per week, the method set forth in (4) of this appendix
may be used:
(1) Negative pressure enclosure/HEPA vacuum system method.
(a) The brake and clutch inspection, disassembly, repair, and assembly
operations shall be enclosed to cover and contain the clutch or brake
assembly and to prevent the release of asbestos fibers into the worker's
breathing zone.
(b) The enclosure shall be sealed tightly and thoroughly inspected
for leaks before work begins on brake and clutch inspection, disassembly,
repair and assembly.
(c) The enclosure shall be such that the worker can clearly see the
operation and shall provide impermeable sleeves through which the worker
can handle the brake and clutch inspection, disassembly, repair and
assembly. The integrity of the sleeves and ports shall be examined before
work begins.
(d) A HEPA-filtered vacuum shall be employed to maintain the enclosure
under negative pressure throughout the operation. Compressed-air may
be used to remove asbestos fibers or particles from the enclosure.
(e) The HEPA vacuum shall be used first to loosen the asbestos containing
residue from the brake and clutch parts and then to evacuate the loosened
asbestos containing material from the enclosure and capture the material
in the vacuum filter.
(f) The vacuum's filter, when full, shall be first wetted with a fine
mist of water, then removed and placed immediately in an impermeable
container, labeled according to WAC 296-62-07721 (6) and disposed of
according to WAC 296-62-07723.
(g) Any spills or releases of asbestos containing waste material from
inside of the enclosure or vacuum hose or vacuum filter shall be immediately
cleaned up and disposed of according to WAC 296-62-07723.
(2) Low pressure/wet cleaning method.
(a) A catch basin shall be placed under the brake assembly, positioned
to avoid splashes and spills.
(b) The reservoir shall contain water containing an organic solvent
or wetting agent. The flow of liquid shall be controlled such that the
brake assembly is gently flooded to prevent the asbestos-containing
brake dust from becoming airborne.
(c) The aqueous solution shall be allowed to flow between the brake
drum and brake support before the drum is removed.
(d) After removing the brake drum, the wheel hub and back of the brake
assembly shall be thoroughly wetted to suppress dust.
(e) The brake support plate, brake shoes and brake components used
to attach the brake shoes shall be thoroughly washed before removing
the old shoes.
(f) In systems using filters, the filters, when full, shall be first
wetted with a fine mist of water, then removed and placed immediately
in an impermeable container, labeled according to WAC 296-62-07721 (6)
and disposed of according to WAC 296-62-07723.
(g) Any spills of asbestos-containing aqueous solution or any asbestos-containing
waste material shall be cleaned up immediately and disposed of according
to WAC 296-62-07723.
(h) The use of dry brushing during low pressure/wet cleaning operations
is prohibited.
(3) Equivalent methods. An equivalent method is one which has sufficient
written detail so that it can be reproduced and has been demonstrated
that the exposures resulting from the equivalent method are equal to or
less than the exposure which would result from the use of the method described
in subsection (1) of this appendix. For purposes of making this comparison,
the employer shall assume that exposures resulting from the use of the
method described in subsection (1) of this appendix shall not exceed 0.016
f/cc, as measured by the WISHA reference method and as averaged over at
least 18 personal samples.
(4) Wet method.
(a) A spray bottle, hose nozzle, or other implement capable of delivering
a fine mist of water or amended water or other delivery system capable
of delivering water at low pressure, shall be used to first thoroughly
wet the brake and clutch parts. Brake and clutch components shall then
be wiped clean with a cloth.
(b) The cloth shall be placed in an impermeable container, labeled
according to WAC 296-62-07721 (6) and then disposed of according to
WAC 296-62-07723, or the cloth shall be laundered in a way to prevent
the release of asbestos fibers in excess of 0.1 fiber per cubic centimeter
of air.
(c) Any spills of solvent or any asbestos containing waste material
shall be cleaned up immediately according to WAC 296-62-07723.
(d) The use of dry brushing during the wet method operations is prohibited.
WAC 296-62-07747
Appendix G--Substance technical information for asbestos--Nonmandatory.
(1) Substance identification.
(a) Substance: “Asbestos” is the name of a class of magnesium-silicate
minerals that occur in fibrous form. Minerals that are included in this
group are chrysotile, crocidolite, amosite, tremolite asbestos, anthophyllite
asbestos, and actinolite asbestos.
(b) Asbestos is used in the manufacture of heat-resistant clothing,
automotive brake and clutch linings, and a variety of building materials
including floor tiles, roofing felts, ceiling tiles, asbestos-cement
pipe and sheet, and fire-resistant drywall. Asbestos is also present
in pipe and boiler insulation materials, and in sprayed-on materials
located on beams, in crawlspaces, and between walls.
(c) The potential for a product containing asbestos, tremolite, anthophyllite,
and actinolite to release breathable fibers depends on its degree of
friability. Friable means that the material can be crumbled with hand
pressure and is therefore likely to emit fibers. The fibrous or fluffy
sprayed-on materials used for fireproofing, insulation, or sound proofing
are considered to be friable, and they readily release airborne fibers
if disturbed. Materials such as vinyl-asbestos floor tile or roofing
felts are considered nonfriable and generally do not emit airborne fibers
unless subjected to sanding or sawing operations. Asbestos-cement pipe
or sheet can emit airborne fibers if the materials are cut or sawed,
or if they are broken during demolition operations.
(d) Permissible exposure: Exposure to airborne asbestos fibers may
not exceed 0.1 fiber per cubic centimeter of air (0.1 f/cc) averaged
over the eight-hour workday (time weighted average), or 1 fiber per
cubic centimeter of air (1 f/cc) during any thirty minute period, (excursion
limit).
(2) Health hazard data.
(a) Asbestos can cause disabling respiratory disease and various types
of cancers if the fibers are inhaled. Inhaling or ingesting fibers from
contaminated clothing or skin can also result in these diseases. The
symptoms of these diseases generally do not appear for twenty or more
years after initial exposure.
(b) Exposure to asbestos has been shown to cause lung cancer, mesothelioma,
and cancer of the stomach and colon. Mesothelioma is a rear cancer of
the thin membrane lining of the chest and abdomen. Symptoms of mesothelioma
include shortness of breath, pain in the walls of the chest, and/or
abdominal pain.
(3) Respirators and protective clothing.
(a) Respirators: You are required to wear a respirator when performing
tasks that result in asbestos exposure that exceeds 0.1 fiber per cubic
centimeter of air (0.1 f/cc) as an eight-hour time weighted average
and/or 1.0 fiber per cubic centimeter (1 f/cc) during any thirty minute
period (excursion limit). These conditions can occur while your employer
is in the process of installing engineering controls to reduce asbestos
exposure, or where engineering controls are not feasible to reduce asbestos
exposure. Air-purifying respirators equipped with a high-efficiency
particulate air (HEPA) filter can be used where airborne asbestos fiber
concentrations do not exceed 1 f/cc; otherwise, air-supplied, positive-pressure,
full facepiece respirators must be used. Disposable respirators or dust
masks are not permitted to be used for asbestos work. For effective
protection, respirators must fit your face and head snugly. Your employer
is required to conduct fit tests when you are first assigned a respirator
and every six months thereafter. Respirators should not be loosened
or removed in work situations where their use is required.
(b) Protective clothing: You are required to wear protective clothing
in work areas where asbestos fiber concentrations exceed the permissible
exposure limits to prevent contamination of the skin. Where protective
clothing is required, your employer must provide you with clean garments.
Unless you are working on a large asbestos removal or demolition project,
your employer must also provide a change room and separate lockers for
your street clothes and contaminated work clothes. If you are working
on a large asbestos removal or demolition project, and where it is feasible
to do so, your employer must provide a clean room, shower, and decontamination
room contiguous to the work area. When leaving the work area, you must
remove contaminated clothing before proceeding to the shower. If the
shower is not adjacent to the work area, you must vacuum your clothing
before proceeding to the change room and shower. To prevent inhaling
fibers in contaminated change rooms and showers, leave your respirator
on until you leave the shower and enter the clean change room.
(4) Disposal procedures and cleanup.
(a) Wastes that are generated by processes where asbestos is present
include:
(i) Empty asbestos shipping containers.
(ii) Process wastes such as cuttings, trimmings, or reject material.
(iii) Housekeeping waste from sweeping or HEPA vacuuming.
(iv) Asbestos fireproofing or insulating material that is removed
from buildings.
(v) Building products that contain asbestos removed during building
renovation or demolition.
(vi) Contaminated disposable protective clothing.
(b) Empty shipping bags can be flattened under exhaust hoods and packed
into airtight containers for disposal. Empty shipping drums are difficult
to clean and should be sealed.
(c) Vacuum bags or disposable paper filters should not be cleaned,
but should be sprayed with a fine water mist and placed into a labeled
waste container.
(d) Process waste and housekeeping waste should be wetted with water
or a mixture of water and surfactant prior to packaging in disposable
containers.
(e) Material containing asbestos that is removed from buildings must
be disposed of in leaktight 6-mil thick plastic bags, plastic-lined
cardboard containers, or plastic-lined metal containers. These wastes,
which are removed while wet, should be sealed in containers before they
dry out to minimize the release of asbestos fibers during handling.
(5) Access to information.
(a) Each year, your employer is required to inform you of the information
contained in this standard and appendices for asbestos. In addition,
your employer must instruct you in the proper work practices for handling
materials containing asbestos and the correct use of protective equipment.
(b) Your employer is required to determine whether you are being exposed
to asbestos. You or your representative has the right to observe employee
measurements and to record the results obtained. Your employer is required
to inform you of your exposure, and, if you are exposed above the permissible
limits, he or she is required to inform you of the actions that are
being taken to reduce your exposure to within the permissible limits.
(c) Your employer is required to keep records of your exposures and
medical examinations. These exposure records must be kept for at least
thirty years. Medical records must be kept for the period of your employment
plus thirty years.
(d) Your employer is required to release your exposure and medical
records to your physician or designated representative upon your written
request.
WAC 296-62-07749
Appendix H--Medical surveillance guidelines for asbestos--Nonmandatory.
(1) Route of entry inhalation, ingestion.
(2) Toxicology.
Clinical evidence of the adverse effects associated with exposure to
asbestos is present in the form of several well-conducted epidemiological
studies of occupationally exposed workers, family contacts of workers,
and persons living near asbestos mines. These studies have shown a definite
association between exposure to asbestos and an increased incidence
of lung cancer, pleural and peretoneal mesothelioma, gastrointestinal
cancer, and asbestosis. The latter is a disabling fibrotic lung disease
that is caused only by exposure to asbestos. Exposure to asbestos has
also been associated with an increased incidence of esophageal, kidney,
laryngeal, pharyngeal, and buccal cavity cancers. As with other known
chronic occupational diseases, disease associated with asbestos generally
appears about twenty years following the first occurrence of exposure:
There are no known acute effects associated with exposure to asbestos.
Epidemiological studies indicate that the risk of lung cancer among
exposed workers who smoke cigarettes is greatly increased over the risk
of lung cancer among nonexposed smokers or exposed nonsmokers. These
studies suggest that cessation of smoking will reduce the risk of lung
cancer for a person exposed to asbestos but will not reduce it to the
same level of risk as that existing for an exposed worker who has never
smoked.
(3) Signs and symptoms of exposure-related disease.
The signs and symptoms of lung cancer or gastrointestinal cancer induced
by exposure to asbestos are not unique, except that a chest x-ray of
an exposed patient with lung cancer may show pleural plaques, pleural
calcification, or pleural fibrosis. Symptoms characteristic of mesothelioma
include shortness of breath, pain in the walls of the chest, or abdominal
pain. Mesothelioma has a much longer latency period compared with lung
cancer (forty years versus fifteen to twenty years), and mesothelioma
is therefore more likely to be found among workers who were first exposed
to asbestos at an early age. Mesothelioma is always fatal.
Asbestosis is pulmonary fibrosis caused by the accumulation of asbestos
fibers in the lungs. Symptoms include shortness of breath, coughing,
fatigue, and vague feelings of sickness. When the fibrosis worsens,
shortness of breath occurs even at rest. The diagnosis of asbestosis
is based on a history of exposure to asbestos, the presence of characteristic
radiologic changes, endinspiratory crackles (rales), and other clinical
features of fibrosing lung disease. Pleural plaques and thickening are
observed on x-rays taken during the early stages of the disease. Asbestosis
is often a progressive disease even in the absence of continued exposure,
although this appears to be a highly individualized characteristic.
In severe cases, death may be caused by respiratory or cardiac failure.
(4) Surveillance and preventive considerations.
As noted above, exposure to asbestos has been linked to an increased
risk of lung cancer, mesothelioma, gastrointestinal cancer, and asbestosis
among occupationally exposed workers. Adequate screening tests to determine
an employee's potential for developing serious chronic diseases, such
as cancer, from exposure to asbestos do not presently exist. However,
some tests, particularly chest x-rays and pulmonary function tests,
may indicate that an employee has been overexposed to asbestos increasing
his or her risk of developing exposure-related chronic diseases. It
is important for the physician to become familiar with the operating
conditions in which occupational exposure to asbestos is likely to occur.
This is particularly important in evaluating medical and work histories
and in conducting physical examinations. When an active employee has
been identified as having been overexposed to asbestos measures taken
by the employer to eliminate or mitigate further exposure should also
lower the risk of serious long-term consequences.
The employer is required to institute a medical surveillance program
for all employees who are or will be exposed to asbestos at or above
the permissible exposure limits (0.1 fiber per cubic centimeter of air)
for 30 or more days per year and for all employees who are assigned
to wear a negative pressure respirator. All examinations and procedures
must be performed by or under the supervision of a licensed physician,
at a reasonable time and place, and at no cost to the employee.
Although broad latitude is given to the physician in prescribing specific
tests to be included in the medical surveillance program, WISHA requires
inclusion of the following elements in the routine examination:
(a) Medical and work histories with special emphasis directed to symptoms
of the respiratory system, cardiovascular system, and digestive tract.
(b) Completion of the respiratory disease questionnaire contained in
WAC 296-62-07741, Appendix D.
(c) A physical examination including a chest roentgenogram and pulmonary
function test that includes measurement of the employee's forced vital
capacity (FVC) and forced expiratory volume at one second (FEV1).
(d) Any laboratory or other test that the examining physician deems
by sound medical practice to be necessary.
The employer is required to make the prescribed tests available at
least annually to those employees covered; more often than specified
if recommended by the examining physician; and upon termination of employment.
The employer is required to provide the physician with the following
information: A copy of this standard and appendices; a description of
the employee's duties as they relate to asbestos exposure; the employee's
representative level of exposure to asbestos; a description of any personal
protective and respiratory equipment used; and information from previous
medical examinations of the affected employee that is not otherwise
available to the physician. Making this information available to the
physician will aid in the evaluation of the employee's health in relation
to assigned duties and fitness to wear personal protective equipment,
if required.
The employer is required to obtain a written opinion from the examining
physician containing the results of the medical examination; the physician's
opinion as to whether the employee has any detected medical conditions
that would place the employee at an increased risk of exposure-related
disease; any recommended limitations on the employee or on the use of
personal protective equipment; and a statement that the employee has
been informed by the physician of the results of the medical examination
and of any medical conditions related to asbestos exposure that require
further explanation or treatment. This written opinion must not reveal
specific findings or diagnoses unrelated to exposure to asbestos and
a copy of the opinion must be provided to the affected employee.
WAC 296-62-07751
Appendix I--Work practices and engineering controls for Class I asbestos
operations--Nonmandatory.
This is a nonmandatory appendix to the asbestos standards for construction
and for shipyards. It describes criteria and procedures for erecting and
using negative pressure enclosures for Class I Asbestos Work, when NPEs
are used as an allowable control method to comply with WAC 296-62-07712
(7)(a). Many small and variable details are involved in the erection of
a negative pressure enclosure. OSHA and most participants in the rulemaking
agreed that only the major, more performance oriented criteria should
be made mandatory. These criteria are set out in WAC 296-62-07712.
In addition, this appendix includes these mandatory specifications and
procedures in its guidelines in order to make this appendix coherent and
helpful. The mandatory nature of the criteria which appear in the regulatory
text is not changed because they are included in this “nonmandatory” appendix.
Similarly, the additional criteria and procedures included as guidelines
in the appendix, do not become mandatory because mandatory criteria are
also included in these comprehensive guidelines.
In addition, none of the criteria, both mandatory and recommended, are
meant to specify or imply the need for use of patented or licensed methods
or equipment. Recommended specifications included in this attachment should
not discourage the use of creative alternatives which can be shown to
reliably achieve the objectives of negative-pressure enclosures.
Requirements included in this appendix, cover general provisions to be
followed in all asbestos jobs, provisions which must be followed for all
Class I asbestos jobs, and provisions governing the construction and testing
of negative pressure enclosures. The first category includes the requirement
for use of wet methods, HEPA vacuums, and immediate bagging of waste;
Class I work must conform to the following provisions:
- oversight by competent person
- use of critical barriers over all openings to work area
- isolation of HVAC systems
- use of impermeable dropcloths and coverage of all objects within
regulated areas
In addition, more specific requirements for NPEs include:
- maintenance of -0.02 inches water gauge within enclosure
- manometric measurements
- air movement away from employees performing removal work
- smoke testing or equivalent for detection of leaks and air direction
- deactivation of electrical circuits, if not provided with ground-fault
circuit interrupters.
Planning the Project
The standard requires that an exposure assessment be conducted before
the asbestos job is begun WAC 296-62-07709(3). Information needed for
that assessment, includes data relating to prior similar jobs, as applied
to the specific variables of the current job. The information needed to
conduct the assessment will be useful in planning the project, and in
complying with any reporting requirements under this standard, when significant
changes are being made to a control system listed in the standard, (see
WAC 296-62-07719), as well as those of USEPA (40 CFR Part 61, subpart
M). Thus, although the standard does not explicitly require the preparation
of a written asbestos removal plan, the usual constituents of such a plan,
i.e., a description of the enclosure, the equipment, and the procedures
to be used throughout the project, must be determined before the enclosure
can be erected. The following information should be included in the planning
of the system:
A physical description of the work area;
A description of the approximate amount of material to be removed;
A schedule for turning off and sealing existing ventilation systems;
Personnel hygiene procedures;
A description of personal protective equipment and clothing to be
worn by employees;
A description of the local exhaust ventilation systems to be used
and how they are to be tested;
A description of work practices to be observed by employees;
An air monitoring plan;
A description of the method to be used to transport waste material;
and
The location of the dump site.
Materials and Equipment Necessary for Asbestos Removal
Although individual asbestos removal projects vary in terms of the equipment
required to accomplish the removal of the materials, some equipment and
materials are common to most asbestos removal operations.
Plastic sheeting used to protect horizontal surfaces, seal HVAC openings
or to seal vertical openings and ceilings should have a minimum thickness
of 6 mils. Tape or other adhesive used to attach plastic sheeting should
be of sufficient adhesive strength to support the weight of the material
plus all stresses encountered during the entire duration of the project
without becoming detached from the surface.
Other equipment and materials which should be available at the beginning
of each project are:
- HEPA Filtered Vacuum is essential for cleaning the work area after
the asbestos has been removed. It should have a long hose capable of
reaching out-of-the-way places, such as areas above ceiling tiles, behind
pipes, etc.
- Portable air ventilation systems installed to provide the negative
air pressure and air removal from the enclosure must be equipped with
a HEPA filter. The number and capacity of units required to ventilate
an enclosure depend on the size of the area to be ventilated. The filters
for these systems should be designed in such a manner that they can
be replaced when the air flow volume is reduced by the build-up of dust
in the filtration material. Pressure monitoring devices with alarms
and strip chart recorders attached to each system to indicate the pressure
differential and the loss due to dust buildup on the filter are recommended.
- Water sprayers should be used to keep the asbestos material as saturated
as possible during removal; the sprayers will provide a fine mist that
minimizes the impact of the spray on the material.
- Water used to saturate the asbestos containing material can be amended
by adding at least 15 milliliters (0.5 ounce) of wetting agent in 1
liter (1 pint) of water. An example of a wetting agent is a 50/50 mixture
of polyoxyethylene ether and polyoxyethylene polyglycol ester.
- Backup power supplies are recommended, especially for ventilation
systems.
- Shower and bath water should be with mixed hot and cold water faucets.
Water that has been used to clean personnel or equipment should either
be filtered or be collected and discarded as asbestos waste. Soap and
shampoo should be provided to aid in removing dust from the workers'
skin and hair.
- See WAC 296-62-07715 and 296-62-07717 for appropriate respiratory
protection and protective clothing.
- See WAC 296-62-07721 for required signs and labels.
Preparing the Work Area
Disabling HVAC Systems: The power to the heating, ventilation, and air
conditioning systems that service the restricted area must be deactivated
and locked off. All ducts, grills, access ports, windows and vents must
be sealed off with two layers of plastic to prevent entrainment of contaminated
air.
Operating HVAC Systems in the Restricted Area: If components of a HVAC
system located in the restricted area are connected to a system that will
service another zone during the project, the portion of the duct in the
restricted area must be sealed and pressurized. Necessary precautions
include caulking the duct joints, covering all cracks and openings with
two layers of sheeting, and pressurizing the duct throughout the duration
of the project by restricting the return air flow. The power to the fan
supplying the positive pressure should be locked “on” to prevent pressure
loss.
Sealing Elevators: If an elevator shaft is located in the restricted
area, it should be either shut down or isolated by sealing with two layers
of plastic sheeting. The sheeting should provide enough slack to accommodate
the pressure changes in the shaft without breaking the air-tight seal.
Removing Mobile Objects: All movable objects should be cleaned and removed
from the work area before an enclosure is constructed unless moving the
objects creates a hazard. Mobile objects will be assumed to be contaminated
and should be either cleaned with amended water and a HEPA vacuum and
then removed from the area or wrapped and then disposed of as hazardous
waste.
Cleaning and Sealing Surfaces: After cleaning with water and a HEPA vacuum,
surfaces of stationary objects should be covered with two layers of plastic
sheeting. The sheeting should be secured with duct tape or an equivalent
method to provide a tight seal around the object.
Bagging Waste: In addition to the requirement for immediate bagging of
waste for disposal, it is further recommended that the waste material
be double-bagged and sealed in plastic bags designed for asbestos disposal.
The bags should be stored in a waste storage area that can be controlled
by the workers conducting the removal. Filters removed from air handling
units and rubbish removed from the area are to be bagged and handled as
hazardous waste.
Constructing the Enclosure
The enclosure should be constructed to provide an air-tight seal around
ducts and openings into existing ventilation systems and around penetrations
for electrical conduits, telephone wires, water lines, drain pipes, etc.
Enclosures should be both airtight and watertight except for those openings
designed to provide entry and/or air flow control.
Size: An enclosure should be the minimum volume to encompass all of the
working surfaces yet allow unencumbered movement by the worker(s), provide
unrestricted air flow past the worker(s), and ensure walking surfaces
can be kept free of tripping hazards.
Shape: The enclosure may be any shape that optimizes the flow of ventilation
air past the worker(s).
Structural Integrity: The walls, ceilings and floors must be supported
in such a manner that portions of the enclosure will not fall down during
normal use.
Openings: It is not necessary that the structure be airtight; openings
may be designed to direct air flow. Such openings should be located at
a distance from active removal operations. They should be designed to
draw air into the enclosure under all anticipated circumstances. In the
event that negative pressure is lost, they should be fitted with either
HEPA filters to trap dust or automatic trap doors that prevent dust from
escaping the enclosure. Openings for exits should be controlled by an
airlock or a vestibule.
Barrier Supports: Frames should be constructed to support all unsupported
spans of sheeting.
Sheeting: Walls, barriers, ceilings, and floors should be lined with
two layers of plastic sheeting having a thickness of at least 6 mil.
Seams: Seams in the sheeting material should be minimized to reduce the
possibilities of accidental rips and tears in the adhesive or connections.
All seams in the sheeting should overlap, be staggered and not be located
at corners or wall-to-floor joints.
Areas Within an Enclosure: Each enclosure consists of a work area, a
decontamination area, and waste storage area. The work area where the
asbestos removal operations occur should be separated from both the waste
storage area and the contamination control area by physical curtains,
doors, and/or airflow patterns that force any airborne contamination back
into the work area.
See WAC 296-62-07719 for requirements for hygiene facilities.
During egress from the work area, each worker should step into the equipment
room, clean tools and equipment, and remove gross contamination from clothing
by wet cleaning and HEPA vacuuming. Before entering the shower area, foot
coverings, head coverings, hand coverings, and coveralls are removed and
placed in impervious bags for disposal or cleaning. Airline connections
from airline respirators with HEPA disconnects and power cables from powered
air-purifying respirators (PAPRs) will be disconnected just prior to entering
the shower room.
Establishing Negative Pressure Within the Enclosure
Negative Pressure: Air is to be drawn into the enclosure under all anticipated
conditions and exhausted through a HEPA filter for 24 hours a day during
the entire duration of the project.
Air Flow Tests: Air flow patterns will be checked before removal operations
begin, at least once per operating shift and any time there is a question
regarding the integrity of the enclosure. The primary test for air flow
is to trace air currents with smoke tubes or other visual methods. Flow
checks are made at each opening and at each doorway to demonstrate that
air is being drawn into the enclosure and at each worker's position to
show that air is being drawn away from the breathing zone.
Monitoring Pressure Within the Enclosure: After the initial air flow
patterns have been checked, the static pressure must be monitored within
the enclosure. Monitoring may be made using manometers, pressure gauges,
or combinations of these devices. It is recommended that they be attached
to alarms and strip chart recorders at points identified by the design
engineer.
Corrective Actions: If the manometers or pressure gauges demonstrate
a reduction in pressure differential below the required level, work should
cease and the reason for the change investigated and appropriate changes
made. The air flow patterns should be retested before work begins again.
Pressure Differential: The design parameters for static pressure differentials
between the inside and outside of enclosures typically range from 0.02
to 0.10 inches of water gauge, depending on conditions. All zones inside
the enclosure must have less pressure than the ambient pressure outside
of the enclosure (-0.02 inches water gauge differential). Design specifications
for the differential vary according to the size, configuration, and shape
of the enclosure as well as ambient and mechanical air pressure conditions
around the enclosure.
Air Flow Patterns: The flow of air past each worker shall be enhanced
by positioning the intakes and exhaust ports to remove contaminated air
from the worker's breathing zone, by positioning HEPA vacuum cleaners
to draw air from the worker's breathing zone, by forcing relatively uncontaminated
air past the worker toward an exhaust port, or by using a combination
of methods to reduce the worker's exposure.
Air Handling Unit Exhaust: The exhaust plume from air handling units
should be located away from adjacent personnel and intakes for HVAC systems.
Air Flow Volume: The air flow volume (cubic meters per minute) exhausted
(removed) from the workplace must exceed the amount of makeup air supplied
to the enclosure. The rate of air exhausted from the enclosure should
be designed to maintain a negative pressure in the enclosure and air movement
past each worker. The volume of air flow removed from the enclosure should
replace the volume of the container at every 5 to 15 minutes. Air flow
volume will need to be relatively high for large enclosures, enclosures
with awkward shapes, enclosures with multiple openings, and operations
employing several workers in the enclosure.
Air Flow Velocity: At each opening, the air flow velocity must visibly
“drag” air into the enclosure. The velocity of air flow within the enclosure
must be adequate to remove airborne contamination from each worker's breathing
zone without disturbing the asbestos-containing material on surfaces.
Airlocks: Airlocks are mechanisms on doors and curtains that control
the air flow patterns in the doorways. If air flow occurs, the patterns
through doorways must be such that the air flows toward the inside of
the enclosure. Sometimes vestibules, double doors, or double curtains
are used to prevent air movement through the doorways. To use a vestibule,
a worker enters a chamber by opening the door or curtain and then closing
the entry before opening the exit door or curtain.
Airlocks should be located between the equipment room and shower room,
between the shower room and the clean room, and between the waste storage
area and the outside of the enclosure. The air flow between adjacent rooms
must be checked using smoke tubes or other visual tests to ensure the
flow patterns draw air toward the work area without producing eddies.
Monitoring for Airborne Concentrations
In addition to the breathing zone samples taken as outlined in WAC 296-62-07709,
samples of air should be taken to demonstrate the integrity of the enclosure,
the cleanliness of the clean room and shower area, and the effectiveness
of the HEPA filter. If the clean room is shown to be contaminated, the
room must be relocated to an uncontaminated area.
Samples taken near the exhaust of portable ventilation systems must be
done with care.
General Work Practices
Preventing dust dispersion is the primary means of controlling the spread
of asbestos within the enclosure. Whenever practical, the point of removal
should be isolated, enclosed, covered, or shielded from the workers in
the area. Waste asbestos containing materials must be bagged during or
immediately after removal; the material must remain saturated until the
waste container is sealed.
Waste material with sharp points or corners must be placed in hard air-tight
containers rather than bags.
Whenever possible, large components should be sealed in plastic sheeting
and removed intact.
Bags or containers of waste will be moved to the waste holding area,
washed, and wrapped in a bag with the appropriate labels.
Cleaning the Work Area
Surfaces within the work area should be kept free of visible dust and
debris to the extent feasible. Whenever visible dust appears on surfaces,
the surfaces within the enclosure must be cleaned by wiping with a wet
sponge, brush, or cloth and then vacuumed with a HEPA vacuum.
All surfaces within the enclosure should be cleaned before the exhaust
ventilation system is deactivated and the enclosure is disassembled. An
approved encapsulant may be sprayed onto areas after the visible dust
has been removed.
For
printing
back
to top