Why are designers requesting the BIO
detector in place of CO2 sensors.
The BIO detector indicates space occupancy
and other air contaminants affecting human health and comfort.
It is a better way to ventilate
The BIO detector is an accurate and reliable
way of incorporating Demand-Controlled Ventilation DCV into a
building´s HVAC strategy.
It will also show that the BIO detector is as
good an indicator of space occupancy as a CO2 sensor while also
measuring other contaminants which affect human comfort and health.
Finally, it will detail how proper
ventilation from the BIO detector improves occupant comfort, health
and productivity and saves money for building owners.
CO2 and Demand-Controlled Ventilation
Until now, Indoor Air Quality has been
defined as proper temperature, humidity and CO2 levels.
According to tenants however, offensive
odors, smoke, carpet off-gassing and other Volatile Organic Compunds
VOC have just as much more impact on human comfort, productivity and
Then why is Indoor Air Quality so closely
linked to CO2?
This is due to one ASHRAE standard 62.1.
This standard establishes minimum ventilation
rates of proper Indoor Air Quality, allowing for Demand Controlled
Ventilation DCV which saves on heating and cooling costs by bringing
in outside air only as it is needed.
Standard 62.1 has two procedures for
establishing the ventilation rates - - one based on VOCs and one
based on occupancy.
The occupancy procedure is used most often
due to it straightforward math and the vast majority of those users
choose CO2 sensors to determine the occupancy of the space.
The problem with this method of DCV is that
it ignores the offensive odors and VOCs that may be present even
when the CO2 levels are low.
As stated earlier, Standard 62.1 has two
procedures, one based on occupancy and the other based on VOCs.
The difficulty with the VOC procedure is that
HVAC system designers must use subjective criteria, such as whether
the air quality is acceptable to 80% or more of the buildings
System designers are not comfortable dealing
with these subjective perception-based criteria, so most choose the
CO2 occupancy method, even though it ignores odors and VOCs.
The BIO detector offers the best of two
It uses the VOC procedure of Standard 62.1 to
measure the space, but provides the HVAC system designer with the
straight forward mathematics of the occupancy based ventilation.
What are VOCs and Where Do they Come From
VOCs are chemicals that contain carbon and can be emitted as
gases at room temperature.
VOCs evaporate from substances, such as
cleaning products, adhesives, paints, dry-cleaning fluids and wood
VOCs are also emitted from humans and animals
in their breath, sweat and directly from their skin.
In fact, the largest share of VOCs in an
indoor space is generated by humans, and this is the reason that
VOCs are an accurate indicator of space occupancy.
The True Meaning of Air Quality
VOCs are known to cause eye, nose and throat irritations,
headache, drowsiness, dizziness, nausea, difficulty concentrating
and fatigue; all summarized under the term Sick Building Syndrome.
The importance of detecting the presence of
VOCs in indoor air goes beyond these immediate health concerns.
People judge the quality of the air not just
by how it feels (temperature and humidity), but also by how it
Unfortunately, offensive odors in offices,
kitchens, gymnasiums and restrooms have no impact on CO2 levels.
A tuna fish sandwich left in a desk drawer
over a weekend may not be life threatening, but may smell like it by
These obnoxious odors reduce everyone´s
productivity until the odor is eliminated.
In retail settings customers may leave and
never come back.
Even small amounts can have a very immediate
A single person entering or passing through a
space may deteriorate the air quality due to heavy amounts of
aftershave lotion, cologne, perfume, hand soap, laundry detergent
residue, fabric softeners or residual cigarette smoke.
In these gases a CO2 sensor will not correct
For instance a Circuit Court Judge was
plagued by migraine headaches causing him to suspend proceedings
until his headaches went away.
An BIO-detector installed in the courtroom
discovered that the Judge´s headaches were caused by support staff´s
Proper ventilation reduced the VOCs to
acceptable levels and the judge´s migraines stopped.
In another example, a plastic injection
molding company´s staff was plagued by persistent minor upper
A BIO-detector was installed and the customer
thought it was faulty because the output stayed at maximum no matter
how much outdoor air was admitted to the building.
Subsequent troubleshooting revealed that
a recently installed molding machine had its exhaust vented into
building´s fresh air intake duct by mistake.
Within two weeks of rerouting the exhaust,
all occupant respiratory symptoms disappeared.
A CO2 sensor would not have sensed the
contaminant from the molding machine.
The Financial Benefits of Appropriate
One of the arguments used against VOC
detectors is that because they sense odors and contaminants along
with occupancy, that the building will be over-ventilated and
therefore waste energy.
According to ASHRAE Standard 62.1 however,
VOC detectors allow the building to be appropriately ventilated, not
over-ventilated, and this appropriate ventilation will save building
owners and tenants money in the long run.
Read more about
the BIO detector´s characteristics and energy saving potential >
Project Guide >