(a) “Spray-finishing operations” means
employment of methods wherein organic or inorganic materials
are utilized in dispersed form from deposit on surfaces to be
coated, treated or cleaned. Such methods of deposit may involve
either automatic, manual, or electrostatic deposition but do
not include metal spraying or metallizing, dipping, flow coating,
roller coating, tumbling, centrifuging, or spray washing and
degreasing as conducted in self-contained washing and degreasing
machines or systems.
(b) “Spray booth” spray booths are defined
and described in WAC
296-24-370 through 296-24-37007.
(See sections 103, 104, and 105 of the Standard for Spray Finishing
Using Flammable and Combustible Materials, NFPA No. 33-1969.)
(c) “Spray room” means a room in which
spray-finishing operations not conducted in a spray booth are
performed separately from other areas.
(d) “Minimum maintained velocity” means
the velocity of air movement which must be maintained in order
to meet minimum specified requirements for health and safety.
(2) Location and application. Spray booths or spray rooms are
to be used to enclose or confine all operations. Spray-finishing
operations shall be located as provided in sections 201 through
206 of the Standard for Spray Finishing Using Flammable and Combustible
Materials, NFPA No. 33-1969.
(3) Design and construction of spray booths.
(a) Spray booths shall be designed and constructed in accordance
with WAC
296-24-370 through
296-24-37007 (see sections 301-304 and 306-310 of the Standard
for Spray Finishing Using Flammable and Combustible Materials,
NFPA No. 33-1969), for general construction specifications.
Note: For a more detailed discussion of
fundamentals relating to this subject, see ANSI Z9.2-1960.
(i) Lights, motors, electrical equipment and other sources
of ignition shall conform to the requirements of WAC
296-24-370. (See section 310 and chapter 4 of the Standard
for Spray Finishing Using Flammable and Combustible Materials,
NFPA No. 33-1969.)
(ii) In no case shall combustible material be used in the
construction of a spray booth and supply or exhaust duct connected
to it.
(b) Unobstructed walkways shall not be less than 6 1/2 feet
high and shall be maintained clear of obstruction from any work
location in the booth to a booth exit or open booth front. In
booths where the open front is the only exit, such exits shall
be not less than 3 feet wide. In booths having multiple exits,
such exits shall not be less than 2 feet wide, provided that
the maximum distance from the work location to the exit is 25
feet or less. Where booth exits are provided with doors, such
doors shall open outward from the booth.
(c) Baffles, distribution plates, and dry-type overspray collectors
shall conform to the requirements of WAC
296-24-370. (See sections 304 and 305 of the Standard for
Spray Finishing Using Flammable and Combustible Materials, NFPA
No. 33-1969.)
(i) Overspray filters shall be installed and maintained in
accordance with the requirements of WAC
296-24-370, (See section 305 of the Standard for Spray
Finishing Using Flammable and Combustible Materials, NFPA
No. 33-1969), and shall only be in a location easily accessible
for inspection, cleaning, or replacement.
(ii) Where effective means, independent of the overspray
filters are installed which will result in design air distribution
across the booth cross section, it is permissible to operate
the booth without the filters in place.
(d)(i) For wet or water-wash spray booths, the water-chamber
enclosure, within which intimate contact of contaminated air
and cleaning water or other cleaning medium is maintained,
if made of steel, shall be 18 gauge or heavier and adequately
protected against corrosion.
(ii) Chambers may include scrubber spray nozzles, headers,
troughs, or other devices. Chambers shall be provided with
adequate means for creating and maintaining scrubbing action
for removal of particulate matter from the exhaust air stream.
(e) Collecting tanks shall be of welded steel construction
or other suitable noncombustible material. If pits are used
as collecting tanks, they shall be concrete, masonry, or other
material having similar properties.
(i) Tanks shall be provided with weirs, skimmer plates, or
screens to prevent sludge and floating paint from entering
the pump suction box. Means for automatically maintaining
the proper water level shall also be provided. Fresh water
inlets shall not be submerged. They shall terminate at least
one pipe diameter above the safety overflow level of the tank.
(ii) Tanks shall be so constructed as to discourage accumulation
of hazardous deposits.
(f) Pump manifolds, risers, and headers shall be adequately
sized to insure sufficient water flow to provide efficient operation
of the water chamber.
(4) Design and construction of spray rooms.
(a) Spray rooms, including floors, shall be constructed of
masonry, concrete, or other noncombustible material.
(b) Spray rooms shall have noncombustible fire doors and shutters.
(c) Spray rooms shall be adequately ventilated so that the
atmosphere in the breathing zone of the operator shall be maintained
in accordance with the requirements of (6)(b) of this section.
(d) Spray rooms used for production spray-finishing operations
shall conform to the requirements of spray booths.
(5) Ventilation.
(a) Ventilation shall be provided in accordance with provisions
of WAC
296-24-370, (See chapter 5 of the Standard for Spray Finishing
Using Flammable or Combustible Materials, NFPA No. 33-1969),
and in accordance with the following:
(i) Where a fan plenum is used to equalize or control the
distribution of exhaust air movement through the booth, it
shall be of sufficient strength or rigidity to withstand the
differential air pressure or other superficially imposed loads
for which the equipment is designed and also to facilitate
cleaning. Construction specifications shall be at least equivalent
to those of (5)(c) of this section.
(ii) All fan ratings shall be in accordance with Air Moving
and Conditioning Association Standard Test Code for Testing
Air Moving Devices, Bulletin 210, April 1962.
(b) Inlet or supply ductwork used to transport makeup air to
spray booths or surrounding areas shall be constructed of noncombustible
materials.
(i) If negative pressure exists within inlet ductwork, all
seams and joints shall be sealed if there is a possibility
of infiltration of harmful quantities of noxious gases, fumes,
or mists from areas through which ductwork passes.
(ii) Inlet ductwork shall be sized in accordance with volume
flow requirements and provide design air requirements at the
spray booth.
(iii) Inlet ductwork shall be so supported throughout its
length to sustain at least its own weight plus any negative
pressure which is exerted upon it under normal operating conditions.
(c) Ducts shall be so constructed as to provide structural
strength and stability at least equivalent to sheet steel of
not less than the following thickness:
DIAMETER OR GREATER DIMENSION
(U.S.
gauge)
Up to 8 inches inclusive
No. 24
Over 8 inches to 18 inches
inclusive
No. 22
Over 18 inches to 30 inches
inclusive
No. 20
Over 30 inches
No. 18
(i) Exhaust ductwork shall be adequately supported throughout
its length to sustain its weight plus any normal accumulation
in interior during normal operating conditions and any negative
pressure exerted upon it.
(ii) Exhaust ductwork shall be sized in accordance with good
design practice which shall include consideration of fan capacity,
length of duct, number of turns and elbows, variation in size,
volume, and character of materials being exhausted. See American
National Standard Z9.2-1960 for further details and explanation
concerning elements of design.
(iii) Longitudinal joints in sheet steel ductwork shall be
either lock-seamed, riveted, or welded. For other than steel
construction, equivalent securing of joints shall be provided.
(iv) Circumferential joints in ductwork shall be substantially
fastened together and lapped in the direction of airflow.
At least every fourth joint shall be provided with connecting
flanges, bolted together or of equivalent fastening security.
(v) Inspection or clean-out doors shall be provided for every
9 to 12 feet of running length for ducts up to 12 inches in
diameter, but the distance between clean-out doors may be
greater for larger pipes. (See 8.3.21 of American National
Standard Z9.1-1960.) A clean-out door or doors shall be provided
for servicing the fan, and where necessary, a drain shall
be provided.
(vi) Where ductwork passes through a combustible roof or
wall, the roof or wall shall be protected at the point of
penetration by open space or fire-resistive material between
the duct and the roof or wall. When ducts pass through fire-walls,
they shall be provided with automatic fire dampers on both
sides of the wall, except that three-eighth-inch steel plates
may be used in lieu of automatic fire dampers for ducts not
exceeding 18 inches in diameter.
(vii) Ductwork used for ventilating any process covered in
this standard shall not be connected to ducts ventilating
any other process or any chimney or flue used for conveying
any products of combustion.
(6) Velocity and air flow requirements.
(a) Except where a spray booth has an adequate air replacement
system, the velocity of air into all openings of a spray booth
shall be not less than that specified in Table 14 for the operating
conditions specified. An adequate air replacement system is
one which introduces replacement air upstream or above the object
being sprayed and is so designed that the velocity of air in
the booth cross section is not less than that specified in Table
14 when measured upstream or above the object being sprayed.
Table 14
Minimum Maintained Velocities into Spray Booths
Operating
Airflow Conditions for Object Completely Inside Booth
Crossdraft
f.p.m.
Airflow
Velocities f.p.m.
Design
Range
Electrostatic
and automatic airless operation contained in booth without
operator.
Negligible
50 large booth
100 small booth
50-75
75-125
Air-operated
guns, manual or automatic.
Up to 50
100 large booth
150 small booth
75-125
125-175
Air-operated
guns, manual or automatic.
Up to 100
150 large booth
200 small booth
125-175
150-250
Notes:
(1) Attention is invited to the fact that the effectiveness
of the spray booth is dependent upon the relationship of the depth
of the booth to its height and width.
(2) Crossdrafts can be eliminated through proper design and
such design should be sought. Crossdrafts in excess of 100 fpm
(feet per minute) should not be permitted.
(3) Excessive air pressures result in loss of both efficiency
and material waste in addition to creating a backlash that may
carry overspray and fumes into adjacent work areas.
(4) Booths should be designed with velocity shown in the column
headed “Design.” However, booths operating with velocities
shown in the column headed “Range” are in compliance
with this standard.
(b) In addition to the requirements in (6)(a) of this section
the total air volume exhausted through a spray booth shall be
such as to dilute solvent vapor to at least 25 percent of the
lower explosive limit of the solvent being sprayed. An example
of the method of calculating this volume is given below.
Example: To determine the lower explosive limits of the most
common solvents used in spray finishing, see Table 15. Column
1 gives the number of cubic feet of vapor per gallon of solvent
and column 2 gives the lower explosive limit (LEL) in percentage
by volume of air. Note that the quantity of solvent will be diminished
by the quantity of solids and nonflammable contained in the finish.
To determine the volume of air in cubic feet necessary
to dilute the vapor from 1 gallon of solvent to 25 percent of
the lower explosive limit, apply the following formula:
Dilution volume
4 (100-LEL) (cubic feet of vapor per gallon)
required per
= ____________________________________
gallon of solvent
LEL
Using toluene as the solvent.
(1) LEL of toluene from Table 15, column 2, is 1.4 percent.
(2) Cubic feet of vapor per gallon from Table 15, column 1, is
30.4 cubic feet per gallon.
(3) Dilution volume required =
4 (100-1.4) 30.4
______________ = 8,564 cubic feet.
1.4
(4) To convert to cubic feet per minute of required ventilation,
multiply the dilution volume required per gallon of solvent by
the number of gallons of solvent evaporated per minute.
Table
15
Lower Explosive Limit
of Some Commonly Used Solvents
Solvent
Cubic
feet of Vapor per gallon of liquid at 70°F.
Lower
explosive limit in percent by volume of air at 70°F.
Column
1
Column
2
Acetone
44.0
2.6
Amyl
Acetate (iso)
21.6
1.0*
Amyl
Alcohol (n)
29.6
1.2
Amyl
Alcohol (iso)
29.6
1.2
Benzene
36.8
1.4*
Butyl
Acetate (n)
24.8
1.7
Butyl
Alcohol (n)
35.2
1.4
Butyl
Cellosolve
24.8
1.1
Cellosolve
33.6
1.8
Cellosolve
Acetate
23.2
1.7
Cyclohexanone
31.2
1.1*
1,1
Dichloroethylene
42.4
5.6
1,2
Dichloroethylene
42.4
9.7
Ethyl
Acetate
32.8
2.5
Ethyl
Alcohol
55.2
4.3
Ethyl
Lactate
28.0
1.5*
Methyl
Acetate
40.0
3.1
Methyl
Alcohol
80.8
7.3
Methyl
Cellosolve
40.8
2.5
Methyl
Ethyl Ketone
36.0
1.8
Methyl
n-Propyl Ketone
30.4
1.5
Naphtha
(VM&P) (76° Naphtha) Naphtha (100° Flash)
22.4
0.9
Safety
solvent-Stoddard Solvent
23.2
1.1
Propyl
Acetate(n)
27.2
2.0
Propyl
Acetate (iso)
28.0
1.8
Propyl
Alcohol (n)
44.8
2.1
Propyl
Alcohol (iso)
44.0
2.0
Toluene
30.4
1.4
Turpentine
20.8
0.8
Xylene
(o)
26.4
1.0
* At 212°F
(c)(i) When an operator is in a booth downstream of the object
being sprayed, an air-supplied respirator or other type of
respirator certified by NIOSH under 42 CFR part 84 for the
material being sprayed should be used by the operator.
(ii) Where downdraft booths are provided with doors, such
doors shall be closed when spray painting.
(7) Make-up air.
(a) Clean fresh air, free of contamination from adjacent industrial
exhaust systems, chimneys, stacks, or vents, shall be supplied
to a spray booth or room in quantities equal to the volume of
air exhausted through the spray booth.
(b) Where a spray booth or room receives make-up air through
self-closing doors, dampers, or louvers, they shall be fully
open at all times when the booth or room is in use for spraying.
The velocity of air through such doors, dampers, or louvers
shall not exceed 200 feet per minute. If the fan characteristics
are such that the required air flow through the booth will be
provided, higher velocities through the doors, dampers, or louvers
may be used.
(c)(i) Where the air supply to a spray booth or room is filtered,
the fan static pressure shall be calculated on the assumption
that the filters are dirty to the extent that they require
cleaning or replacement.
(ii) The rating of filters shall be governed by test data
supplied by the manufacturer of the filter. A pressure gauge
shall be installed to show the pressure drop across the filters.
This gauge shall be marked to show the pressure drop at which
the filters require cleaning or replacement. Filters shall
be replaced or cleaned whenever the pressure drop across them
becomes excessive or whenever the air flow through the face
of the booth falls below that specified in Table 14.
(d)(i) Means of heating make-up air to any spray booth or
room, before or at the time spraying is normally performed,
shall be provided in all places where the outdoor temperature
may be expected to remain below 55° F. for appreciable periods
of time during the operation of the booth except where adequate
and safe means of radiant heating for all operating personnel
affected is provided. The replacement air during the heating
seasons shall be maintained at not less than 65° F. at the
point of entry into the spray booth or spray room. When otherwise
unheated make-up air would be at a temperature of more than
10° F. below room temperature, its temperature shall be regulated
as provided in section 3.6 of ANSI Z9.2-1960.
(ii) As an alternative to an air replacement system complying
with the preceding section, general heating of the building
in which the spray room or booth is located may be employed
provided that all occupied parts of the building are maintained
at not less than 65° F. when the exhaust system is in operation
or the general heating system supplemented by other sources
of heat may be employed to meet this requirement.
(iii) No means of heating make-up air shall be located in
a spray booth.
(iv) Where make-up air is heated by coal or oil, the products
of combustion shall not be allowed to mix with the make-up
air, and the products of combustion shall be conducted outside
the building through a flue terminating at a point remote
from all points where make-up air enters the building.
(v) Where make-up air is heated by gas, and the products
of combustion are not mixed with the make-up air but are conducted
through an independent flue to a point outside the building
remote from all points where make-up air enters the building,
it is not necessary to comply with (7)(d)(vi) of this section.
(vi) Where make-up air to any manually operated spray booth
or room is heated by gas and the products of combustion are
allowed to mix with the supply air, the following precautions
must be taken:
(A) The gas must have a distinctive and strong enough odor
to warn workmen in a spray booth or room of its presence
if in an unburned state in the make-up air.
(B) The maximum rate of gas supply to the make-up air heater
burners must not exceed that which would yield in excess
of 200 p.p.m. (parts per million) of carbon monoxide or
2,000 p.p.m. of total combustible gases in the mixture if
the unburned gas upon the occurrence of flame failure were
mixed with all of the make-up air supplied.
(C) A fan must be provided to deliver the mixture of heated
air and products of combustion from the plenum chamber housing
the gas burners to the spray booth or room.
(8) Scope. Spray booths or spray rooms are to be used to enclose
or confine all spray finishing operations covered by this paragraph.
This paragraph does not apply to the spraying of the exteriors
of buildings, fixed tanks, or similar structures, nor to small
portable spraying apparatus not used repeatedly in the same location.
(1) Definition. A lack of sufficient oxygen is deemed to exist
if the atmosphere at sea level has less than 19.5% oxygen by volume
or has a partial pressure of oxygen of 148 millimeters of mercury
(mm Hg) or less. This may deviate when working at higher elevations
and should be determined for an individual location. Factors such
as acclimatization, physical conditions of the persons involved,
etc., must be considered for such circumstances and conditions.
(2) Entering areas with possible oxygen deficient atmospheres.
Workers entering any area where a lack of sufficient oxygen is
probable shall be supplied with and shall use approved equipment
(for specific requirements see applicable provisions of chapters
296-62, 296-307 (Part U-3), 296-809 and 296-841 WAC) capable of
providing safe respirable air, or prior to entry at at all times
when workers are in such areas a sufficient supply of safe, respirable
air shall be provided. All workers so exposed shall be under constant
observation. If the oxygen content is unknown or may change during
occupation, tests shall be required prior to and during occupation
of questionable areas.
Ventilation shall mean the provision, circulation or exhausting
of air into or from an area or space.
(1) "Local exhaust ventilation"
shall mean the mechanical removal of contaminated air from the
point where the contaminant is being generated or liberated.
(2) "Dilution ventilation"
means inducing and mixing uncontaminated air with contaminated
air in such quantities that the resultant mixture in the breathing
zone will not exceed the permissible exposure limit (PEL) specified
for any contaminant.
(3) "Exhaust ventilation"
means the general movement of air out of the area or permit-required
confined space by mechanical or natural means.
(4) "Tempered make-up air"
means air which has been conditioned by changing its heat content
to obtain a specific desired temperature.
In addition to those mandatory controls as set forth in WAC 296-62-11019,
chapter 296-818 WAC, Abrasive blasting, chapter 296-835 WAC, Dipping
and coating operations (dip tanks), the Industrial Ventilation
Manual of Recommended Practices as compiled and approved
by the American Conference of Governmental Industrial Hygienists,
applicable ANSI Standard or other National Consensus Standards
recommended by the federal government, should be used as a guide
for ventilation requirements.
Exhaust from ventilation systems shall discharge in such a manner
that the contaminated air being exhausted will not present a health
hazard to any workman or reenter buildings in harmful amounts.
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