VOC Gas Sensors Flyer Datasheet by Sensirion AG

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SENSIRION
Experts in Environmental Sensing
Indoor Air Quality and
Volatile Organic Compounds
Summary
Awareness of the importance of good air quality in our living and working environments is becoming increasingly important to individuals
and governments. People spend 90 % of their time indoors where VOCs account for one of the main contributors to bad air quality.
Sensirion’s VOC measurement concept has been established as a practical time and cost-effective method of surveying indoor environ-
ments for contamination. Sensirion’s SGP40 VOC sensor enables measurement of VOC events and thus helps to increase the efficiency
of ventilation and air purification, and increases awareness of VOC sources and indoor air pollution.
VOCs are one of the main contributors to bad air quality. Modern
building materials and methods result in better insulation, and
thus improved energy efficiency, but on the other hand they limit
the air exchange with the outside world and hence lead to higher
VOC concentrations indoors. Exposure to high and/or hazardous
levels of VOCs can be avoided by appropriate ventilation or by
identifying and eliminating the pollution source. Nowadays, most
people spend more than 20 hours per day indoors where VOC
concentrations are more than five times higher than outdoor
concentrations1.
VOCs originate from a number of different possible sources, like
building materials, tobacco smoke, people and their activities,
and indoor chemical reactions. Exceptionally high VOC levels are
typically found in new buildings or after renovation. Further, when
using products that contain VOCs, such as air fresheners or clean-
ing agents, people expose themselves and others to high pollutant
levels that can persist long after the activity has finished. VOCs
include a wide range of chemical compounds, the most common
of which are listed in Table 1 below.
Typical VOC Sources Compound Class Example Compounds
Cleaning agents Aliphatic hydrocarbons, organochlorides Tetrachloroethylene
Solvents Aliphatic and aromatic hydrocarbons Heptane, decane, toluene, xylene
Cosmetics Terpenes, ketones Eucalyptol, limonene
Consumer products Terpenes, aromatic hydrocarbons Limonene, α-Pinene, toluene
Carpets and flooring Esters, aliphatic and aromatic hydrocarbons Butylacetate, heptane
Paints Alcohols, aldehydes Isobutanol
Human occupants Acetone, methanol, ethanol
Table 1 Typical indoor VOCs and their sources 2
1 EPA – the total exposure assessment methology (TEAM) study (1987), Saarela et al., Atmosph. Environ. 37, 5563 (2003)
2 See e.g. Kataoka et al. – Chap. 9 in Mass Spectrometry, Advanced Gas Chromatography – Progress in Agricultural, Biomedical and Industrial Applications (2012)
What are VOCs?
VENTILATION
Regular ventilation is an effective
way to reduce exposure to VOCs.
This can be done either by an auto-
matic demand-controlled venti-
lation system equipped with suitable
sensors, or by natural ventilation
through open windows and doors.
SOURCE CONTROL
Most national governmental bodies
provide guidelines and recommenda-
tions on avoiding and removing
VOC sources in indoor environments6.
Steps to Reduce VOC Levels
SENSORY IRRITATION
A number of systematic human exposure
studies have shown various adverse health
effects caused by exposure to elevated VOC
levels3. Among the effects reported by par-
ticipants are dryness and irritation of the
eye, the nose and the throat, headaches,
and dizziness.
COGNITIVE ABILITIES
Poor indoor air quality can lead to decreased
cognitive function resulting in significant
impacts on productivity, learning, and safety.
Recent studies have demonstrated clear
negative effects of elevated VOC levels on
cognitive abilities such as strategic thinking
and decision making4.
SICK BUILDING SYNDROME
The sick building syndrome5 includes a
variety of health and comfort effects
associated with the time spent in buildings
with, among other factors, elevated VOC
levels. Symptoms of the sick building syn-
drome include headaches, mucous mem-
brane irritation, asthma-like symptoms, skin
irritation and dryness.
Potential Health Effects of High VOC Concentrations
3 Molhave, Indoor Air 4, 357 (1991), Kjaergaard et al. Atmosph. Environ. 25a, 14 17- 1426 (1991), Otto et al, Neurotoxicol. Teratol., 12, 649 (1990)
4 Allen et al., Environ. Health Perspect. 124, 805 (2016)
5 Godish, T.: Sick Buildings – Definition, Diagnosis and Mitigation, Boca Raton: Lewis Publishers (1995)
6 See e.g., https://www.epa.gov/indoor-air-quality-iaq/volatile-organic-compounds-impact-indoor-air-quality
AIR PURIFICATION
Air cleaning devices equipped with
suitable filters are an effective
way to reduce the concentration of
VOCs in indoor air, in particular
in locations where ventilation with
outside air is not appropriate.
less intense man average more Inlense man average <—> 4—) 1 1 DD 500 average
Sensirion’s VOC Measurement
The Benefits of Measuring VOCs
An effective reduction of VOC exposure requires monitoring of the evolution of VOC levels using suitable sensors. A large number of
applications such as ventilation controls, air purifiers, or Internet-of-Things devices benefit from the integration of VOC sensors.
CREATE AWARENESS
Indication of the indoor VOC levels helps
people to better understand their living en-
vironment and to identify possible sources
of indoor air pollutants.
MAKE DEVICES SMARTER
Enable the operation of autonomous de-
vices; for example, automatic operation of
an air purifier.
MAKE DEVICES ENERGY EFFICIENT
Save energy by operating ventilation and air
purification devices only when needed; for
example, demand-controlled ventilation.
Sensirion’s powerful VOC Algorithm analyzes VOC events detect-
ed by the SGP40 sensor and maps them to a VOC Index. This VOC
Index provides a practical quantification of VOC events relative to
each individual sensors average indoor environment. In this way,
it behaves similarly to the human nose, which is highly suscepti-
ble to changes in odor, but it also detects VOC events that are not
perceived by humans. The VOC Index indicates to what extent the
indoor air quality has deteriorated (VOC Index > 100) or improved
(VOC Index < 100) compared to the sensor’s average VOC envi-
ronment of the past 24 h.
This information can be used, e.g., for gradually controlling the
fan of an air treatment device or to provide users with feedback
on their daily activity profile.
Figure 1 The indoor air quality can be monitored thanks to the VOC Index output of the SGP40 sensor.
Environmental
Sensing
CO2
VOC PM2.5
RH / T
With the SGP40, Sensirion provides a metal-oxide based VOC
sensor for indoor air quality applications. The sensing element
features an unmatched robustness against contaminating gases
present in real-world applications. This enables a unique long-term
stability and low drift. The SGP40 features a VOC Index signal via
an I2C interface, a small DFN package (2.44 × 2.44 × 0.85 mm3),
and a dust and water protection membrane. Furthermore, the
SGP40 has a low-power consumption of 2.6 mA at 3.3 V. These
characteristics make the SGP40 easy to integrate into a large
variety of applications such as air purifiers or smart home devices.
Sensirion’s sensor solutions provide detailed and reliable data on further key environmental parameters such as humidity, temperature,
particulate matter (PM2.5), and CO2. Sensirion’s portfolio of environmental sensors opens up numerous possibilities to create smarter
devices that improve our comfort and well being, and increase energy efficiency in various applications.
Sensirion’s Environmental Sensor Solutions
1-900061-01 / 2009-VOC-EN
www.sensirion.com

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