Applications
Indoor Air Quality is a function
of several factors of which temperature is the most important thermal comfort
measurement. It is typically controlled between 68°F to 70°F and
(20°C to 25°C), and sudden temperature changes can cause discomfort,
and indirectly affect other comfort parameters such as relative humidity.
By following the air temperature for a week, it is possible to follow a
building’s air handling behavior.
Relative Humidity (Rh) and
dewpoint (absolute humidity) measurements verify conditions are within
a comfortable range for occupants. They also provide data ensuring the
environment is not conducive to microbial growth or verify that laboratories,
computer rooms, storage areas, etc. have acceptable moisture levels. A
low % Rh is not an answer to all IAQ problems since if the % Rh is too
low, eye irritation, skin irritation and respiratory tract problems may
arise. Dust is generally more of a problem in low humidity situations.
Most viruses grow best in low temperature/high humidity conditions. Formaldehyde
emissions also increase when both temperature and Rh increase. Hence, Rh
limits for IAQ purposes are usually specified as being between 30% and
60%.
The Carbon Dioxide (CO2)
concentration level is an important parameter to measure as it provides
a practical basic indicator of ventilation, and accurately calculates outdoor
air ventilation and air dilution rates. As a surrogate indicator of air
quality, CO2 provides a natural tracer through the building’s
ventilation system.
Carbon Monoxide (CO) levels
provide an indication of improperly ventilated combustion processes to
verify occupants are not at risk from this potentially lethal specific
pollutant. This is particularly important where direct-fired heat exchangers
are used. Mechanical damage or corrosion to the heat exchanger causes mixing
of the combustion gas with the return air, resulting in a buildup of CO
inside the building. Inhalation of CO is highly toxic even at relatively
low concentrations, and in high concentrations can cause immediate collapse
and death. Any concentration in excess of a few ppm should be investigated.
The IAQ Surveyor instruments
can be used for quick spot-checks, walk-through surveys, or left to monitor
over time; storing days, weeks, or even months of data. |