VENTILATION
TPR² is a world leader in the research, development and manufacturing of ultra-thin fire protective coatings
for use in a multitude of applications in the construction industry. A number of these coating products have
been successfully tested and approved for use in conjunction with spray polyurethane foam (SPF) in both the
residential and commercial applications. Each coating has its own set of parameters for its approved use including specific application details including temperature and humidity ranges. One factor that is common to
all the coatings is proper ventilation of the ambient space where the coating is being applied. Proper ventilation is crucial for the proper drying and curing of the coating and to ensure it will perform as designed and
tested. These are good manufacturing processes identified by the latex coatings industry. You can learn more
at http://paintgurus.typepad.com/blog/2010/10/index.html
W H Y V E N T I L AT E
Typically, there is no need for specialized ventilation requirements when spraying within the correct temperature and humidity range in an open environment where there is adequate air movement.
Closed areas, such as unvented attics, will require some method of removing the stale humid air and replacing it with fresh
air on a continuing basis during the spraying and drying period. Cross ventilation, while creating a negative pressure
within the enclosed space, is the only effective method of ventilating a space such as an unvented attic. A five gallon pail
of coating will have approximately 16.7 lbs of liquid to evaporate once applied. That amount of evaporation will require
20,800 cubic feet of air to hold the vapor at 60°F while 6,000 cubic feet of air will hold the vapor at 100°F. These figures
are assuming the humidity in the air originates completely from the coating evaporating. Normal ambient temperature and
humidity compounds the problem and high humidity will further negate any effective evaporation; consequently, the coating doesn’t dry properly. When one considers a gabled attic of a 2,000 square foot house with an 8/12 pitch roof will
have an attic space of approximately 13,300 cubic feet, the need for ventilating with exterior air is obvious. The need to
create a negative pressure in the enclosed area is to ensure the humid air that contains the off gassed components of both
the SPF and coating are evacuated to the exterior unoccupied area and not being forced into the occupied/living area.
HOW TO VENTILATE AN ENCLOSED SPACE
The following ventilation technique is required in any environment where there isn’t free air movement across the coated
surface:
Review the temperature and humidity data on the technical data sheet to ensure the work environment is within the
perimeters of the coating being applied. TPR² recommends a temperature range of 62°F to 95°F and a relative humidity of
40% to 60% and no greater than 70%.
Inspect the foam substrate to ensure it is dry, clean and secured to its substrate. Use a moisture meter to ensure the foam
has a moisture level below 19%.
Use a “supply” blower to draft fresh exterior air to one end of the enclosed space via a hose from the non-occupied exterior.
Ensure the supply air flows across the immediate vicinity of the spray operation.
Use an “exhaust” blower to evacuate the stale, moisture laden air from the opposite end of the enclosed space through a
hose to the exterior of the building.
The exhaust blower must have a larger air volume output than the supply blower to ensure the enclosed space is maintained at a negative pressure in relationship to the surround area.
Do not arrange the ends of the hoses where the supply air is drafting air from the exhaust hose.
Do not exhaust the stale air into any living space or garage area. It must be exhausted to a safe uninhabited open area.
Place a filter over the exhaust hose to avoid spreading overspray.
Ensure the lengths of supply and exhaust hoses and filter do not restrict the air movement.
Constantly monitor the humidity and temperature to ensure the spray environment remains within the perimeters
of the coatings data sheet. Continued monitoring of the coating from its initial application until it is thoroughly dry is critical. If the
relative humidity is greater than 60% at the end of spraying and cross ventilation is not drastically reducing it, then mechanical dehumidifier drying is required until the coating is thoroughly dry.
© TPR² Corp., 2013
Page 1 of 2
WHY IS IT SO IMPORTANT TO HAVE PROPER VENTILATION
Impact of temperature and humidity:
Proper ambient air, substrate and coating temperatures
and low humidity are necessary for the adhesion and drying of the coating. As air cools, it loses its ability to
hold water vapor; e.g., 1,000 cubic feet of 90°F air will
hold 2.2 lbs of water while 1,000 cubic feet of 40°F air
will only hold 0.4 lbs of water. On average, TPR²’s
coatings are approximately 60% solids which mean each
gallon of coating has roughly 2/5 gallon or 3.3 lbs of liquid that must be evaporated from each gallon of the applied coating for it to dry and cure. Lower temperature or
higher humidity will inhibit the evaporation rate of the
coating; thus, preventing it from drying properly. A secondary problem associated with the slower drying is the
lingering of the odors associated with the evaporation of
the liquid components. TPR² uses EPA compliant, ultra
low VOC materials in all of its coatings; however, there
are relatively minor nonhazardous odors emitted from the
coating as it dries. Under normal drying conditions these
odors, which are similar to any low-odor latex paint, are
quickly dissipated and do not cause any lingering issues.
The drying and curing process:
The FIRESHELL® product line of coatings is latex based.
In order to ensure latex based coatings are applied properly, it
is important to understand how they dry and cure. As the coating dries, the liquid components within it evaporates. The more
liquid that evaporates from the coating, the more stable and
cured it becomes. The drying time between coats is normally
longer than simply “dry to touch”, especially with thicker coating applications. “Dry to touch” means you can put your hand
on a freshly coated surface without getting paint on your hand.
The liquids have evaporated only from the surface of the paint,
not underneath. It does not mean that the coating is sufficiently
dry enough to add a second coat to the freshly finished surface
without creating significantly longer drying time. Building a
thick coating, intentionally or unintentionally, or spraying the
coating over an uncured substrate may potentially create problems in the drying and curing process. Until all the liquids
have completed evaporated, the coating is not cured. Once
cured, normally two to four weeks, it becomes a durable and
inert fire protective finish. Even under adverse application
conditions, the coating will eventually cure; however, the noncompliant application procedure may affect adhesion quality,
lingering odors, drying time, and the warranty of the coating.
Relative Humidity Vs. Humidity
Humidity, referred to as Absolute Humidity, is the amount of water vapor in the air. Relative Humidity is
the amount of water vapor in the air verses the amount of water vapor the air can hold. Relative Humidity
depends upon the temperature of the air. The air acts like a sponge and absorbs water through the process of
evaporation. Warm air is less dense and therefore the molecules are further spread apart allowing more
moisture between them. Cooler air causes the molecules to draw closer together limiting the amount of water the air can hold. Relative Humidity, expressed as a percent, measures the current Absolute Humidity
relative to the maximum for that temperature. A device to measure humidity is called a Psychrometer.
Fluke 971 temperature and moisture meter is
an ideal instrument for the monitoring of the
workspace to ensure it is within the specs for
spraying of the coating. This quality instrument is available from a number of sources.
Continued monitoring of the coating from
its initial application until it is thoroughly
dry is critical. If the relative humidity is
greater than 60% at the end of spraying
and cross ventilation is not drastically
reducing it, then mechanical dehumidifier
drying is required. The dehumidifier must
be operated until the coating is thoroughly
dry, at least for several days after the coating is sprayed.
An example of an inexpensive blower and
hose assembly. These items are sold by
Northern Tool and Equipment,
(www.northerntool.com) Uninsulated
HVAC flexible duct may be used for ducting the air into and from the workspace. It
is very handy for use in the immediate
spray area, especially while spraying SPF
An industrial dehumidifier.
as it is inexpensive and may be disposed of
after it becomes unusable from overspray. Do not use propane or kerosene heaters to heat a closed space.
Besides the generation of CO and CO², every gallon of fuel
burned will create 91,502 Btu of heat and approximately one gallon of water vapor which will max out the moisture holding capacity of 10,400 cubic feet of air at 60°F.
© TPR² Corp., 2013
Page 2 of 2