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  Updated: 13 Nov 2018


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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 health.

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 occupants.

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 worlds.

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 preservatives.

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 smells.

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 Monday.

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 effects.

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 the problem.

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 cosmetics.

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 respiratory aliments.

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 Ventilation
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 >

Standard - Wall design




Gas Specif.

Tests based on experience





Project Guide >

Duct design


Levels to set in the ventilation system

Measurement starts at 450 ppm. At 10 volt
output signal it becomes approximately 11%
at 4800 ppm and 22% at 0 to 2000 ppm.


Air quality detector with display









Compatible with different types of bus systems

Gas Central for 1-2 sensors (1 built-in) with
relay outputs for 4 alarm levels, internal
buzzer, operator panel and display





Appl. tests







Gas specif.


Warning lights for air quality detectors


Gas alarm plate for air quality detector


Warning Siren for air quality sensors


Combined warning siren and flash light for
air quality sensors





E-mail: ewert@automatikprodukter.se     

Phone: +46(0)31-287202

Mobile: +46(0)708885298



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