Best Practices for the Reduction of Air Emissions From Construction ...

CHEMINFO
• always mix thinner with the coating according to
the manufacturer’s instructions; and
• mixing operations should be undertaken to
minimize the exposure of the coating to air (e.g.,
in sealed containers).
Some coatings manufacturers provide technical data
sheets that include important information about the
proper preparation and application conditions for
their products. This information should be reviewed
when preparing a coatings management plan and
communicated to coatings applicators.
7.4.1.3 Coatings Wastage Through Spillage and
Splashing Should be Minimized
Handling procedures should be designed to minimize
coatings wastage through reduced spillage and
splashing, for instance by adhering to the following:
• During transfers, container lids, bungs, plugs, or
valves may be opened or removed, but should be
replaced or closed immediately after the transfer
is complete;
• If it is necessary to open coating containers for
prolonged periods, the use of flexible coverings
(e.g., plastic film or sheet, fabric cloth) to cover
the surface of the coating should be considered
to minimize VOC losses;
• During transfers of coatings from one container
to another, a pump and hose system should be
used where possible to minimize fugitive VOC
emissions. Vent holes in the source container
should be opened to prevent the creation of a
vacuum that might prevent adequate drainage
and potentially lead to an unexpected large
spillage;
• If manual decanting from one container to
another must be done, it should be performed
slowly and carefully to minimize spillage and
splashing; and
• Where possible, separate pumping systems
should be used for different paint colours to
minimize flushing requirements. If this is not
possible, colour applications should be
sequenced to minimize flushing.
7.4.1.4 Surface to be Coated Should be Properly
Prepared
Well-prepared surfaces will not need an excessive
volume of coatings. Proper surface preparation can
include: (i) removal of undesirable material from the
substrate; (ii) sealing of cracks and fissures; and (iii)
sanding to achieve desirable roughness for proper
coating adhesion. Surfaces to be coated should be
prepared as per the coating manufacturers
specifications. All dirt, rust, scale, splinters, loose
particles, disintegrated paint, grease, oil, and other
substances should be removed from all surfaces that
are to be painted or otherwise finished. Surface
cracks or fissures should be filled with appropriate
solid materials (putty, joint compounds), sealers or
primers to minimize spaces where coatings can
accumulate.
7.4.1.5 Paint Heaters Should be Used Instead of
Paint Thinners
Paint heaters should be used to heat coatings to
reduce viscosity immediately before spraying. Paint
heaters use an in-line heating element located just
upstream of the spray gun. The use of paint heaters
provides the necessary viscosity to the coating
operation, without the use of solvent-based thinners.
It should be noted that the use of paint heaters is not
always applicable. For instance, the application of
heated paint to cold surfaces in winter months results
in poor paint surface characteristics (i.e., cracking)
because of the rapid cooling of the hot paint after it is
applied to the cold surface.
7.4.1.6 Technologically Advanced Spray-Guns
Should be Utilized to Apply Coatings
The most technologically advanced spray-guns
should be utilized in order to apply coatings. VOC
emissions can be significantly reduced by utilizing
the most efficient spray guns with the highest
transfer efficiency. Transfer efficiency is defined as
the ratio of paint that adheres to the surface of the
product to the total amount of paint that leaves the
gun’s nozzle.
Conventional high-pressure spray guns operate
between 30 and 90 psi. The transfer efficiency of
these high-pressure spray guns is poor. The high
pressures associated with these spray guns force paint
Best Practices for the Reduction of Air Emissions From Construction and Demolition Activities 34