<s>
A	O
carbon	B-Algorithm
dioxide	I-Algorithm
sensor	I-Algorithm
or	O
CO2	B-Algorithm
sensor	I-Algorithm
is	O
an	O
instrument	O
for	O
the	O
measurement	O
of	O
carbon	O
dioxide	O
gas	O
.	O
</s>
<s>
The	O
most	O
common	O
principles	O
for	O
CO2	B-Algorithm
sensors	I-Algorithm
are	O
infrared	O
gas	O
sensors	O
(	O
NDIR	O
)	O
and	O
chemical	O
gas	O
sensors	O
.	O
</s>
<s>
NDIR	O
CO2	B-Algorithm
sensors	I-Algorithm
are	O
also	O
used	O
for	O
dissolved	O
CO2	O
for	O
applications	O
such	O
as	O
beverage	O
carbonation	O
,	O
pharmaceutical	O
fermentation	O
and	O
CO2	O
sequestration	O
applications	O
.	O
</s>
<s>
New	O
developments	O
include	O
using	O
microelectromechanical	B-Architecture
systems	I-Architecture
(	O
MEMS	B-Architecture
)	O
IR	O
sources	O
to	O
bring	O
down	O
the	O
costs	O
of	O
this	O
sensor	O
and	O
to	O
create	O
smaller	O
devices	O
(	O
for	O
example	O
for	O
use	O
in	O
air	O
conditioning	O
applications	O
)	O
.	O
</s>
<s>
Most	O
CO2	B-Algorithm
sensors	I-Algorithm
are	O
fully	O
calibrated	O
prior	O
to	O
shipping	O
from	O
the	O
factory	O
.	O
</s>
<s>
Sensors	O
for	O
these	O
substances	O
can	O
be	O
made	O
using	O
cheap	O
(	O
~	O
$20	O
)	O
Microelectromechanical	B-Architecture
systems	I-Architecture
(	O
MEMS	B-Architecture
)	O
metal	B-Architecture
oxide	I-Architecture
semiconductor	I-Architecture
(	O
MOS	O
)	O
technology	O
.	O
</s>
<s>
For	O
HVAC	O
applications	O
,	O
CO2	B-Algorithm
sensors	I-Algorithm
can	O
be	O
used	O
to	O
monitor	O
the	O
quality	O
of	O
air	O
and	O
the	O
tailored	O
need	O
for	O
fresh	O
air	O
,	O
respectively	O
.	O
</s>
