Painting Contractors: Ventilation is Good for You and Your Paint
When applying paints on interior surfaces it is important to consider the
ventilation or airflow in and out of the room.
Solvent based paints can pose a safety and health hazard if there is little
or no ventilation during the application. People with allergies can be subjected
to health related responses ranging from mild asthma to severe headaches
over a relatively short period. This can even come about when using paints
containing the weaker hydrocarbon solvents like stoddard solvent and mineral
spirits which are found in most interior alkyds. Low odor solvents like
the paraffinic napthas can be particularly dangerous as they are difficult
to smell even at relatively high concentrations.
Depending on the type of coating being applied, the solvent based materials
can pose more significant fire dangers. Lacquers contain solvents that are
capable of igniting at temperatures as low as -7° C if exposed to an
open flame or spark in a concentration between the LEL (lower explosive
limit) and UEL (upper explosive limit). Ventilation is a method of keeping
the concentration below the LEL.
Latex paints are less dangerous but also should be well ventilated. The
average latex paint can contain a concentration of 60 - 70 percent by volume
of water. Now, let's assume that it will take five gallons of paint to coat
the interior walls of a room once and that the latex paint used has a volume
solids of 40 percent. When the painting is completed, there will be three
gallons of water that has evaporated into the air. This is a significant rise
in humidity in the air and can hinder the proper curing of the paint.
Most general purpose latex paints contain a co-solvent. This is a powerful,
slow evaporating solvent like Butyl Carbitol (diethylene glycol monobutyl
ether) that assists in fusing the emulsion particles together after most of
the water has evaporated, to form a cohesive film.
Where the evaporation rate of water is affected by the humidity level (high
humidity = slower evaporation rate), the co-solvents are less affected and
tend to evaporate at a constant rate. So, in a high humidity situation, most
of the co-solvent is leaving the film before the water. This can leave the
paint film poorly fused (coalesced) and create problems such as poor
adhesion, water resistance, low film integrity and gloss and color variations
when the water has finally evaporated from the film.
To maximize safety and the film forming properties of a paint application on
an interior surface, a moderate air flow can be the least expensive
tool.
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