<s>
A	O
hydrogen	B-Algorithm
sensor	I-Algorithm
is	O
a	O
gas	O
detector	O
that	O
detects	O
the	O
presence	O
of	O
hydrogen	O
.	O
</s>
<s>
They	O
contain	O
micro-fabricated	O
point-contact	O
hydrogen	B-Algorithm
sensors	I-Algorithm
and	O
are	O
used	O
to	O
locate	O
hydrogen	O
leaks	O
.	O
</s>
<s>
There	O
are	O
various	O
types	O
of	O
hydrogen	B-Algorithm
microsensors	I-Algorithm
,	O
which	O
use	O
different	O
mechanisms	O
to	O
detect	O
the	O
gas	O
.	O
</s>
<s>
Several	O
types	O
of	O
optical	B-Architecture
fibre	I-Architecture
surface	O
plasmon	O
resonance	O
(	O
SPR	O
)	O
sensor	O
are	O
used	O
for	O
the	O
point-contact	O
detection	O
of	O
hydrogen	O
:	O
</s>
<s>
Fiber	B-Device
Bragg	I-Device
grating	I-Device
coated	O
with	O
a	O
palladium	O
layer	O
–	O
Detects	O
the	O
hydrogen	O
by	O
metal	O
hindrance	O
.	O
</s>
<s>
Electrochemical	O
hydrogen	B-Algorithm
sensor	I-Algorithm
–	O
low	O
(	O
ppm	O
)	O
levels	O
of	O
hydrogen	O
gas	O
can	O
be	O
sensed	O
using	O
electrochemical	O
sensors	O
which	O
comprise	O
an	O
array	O
of	O
electrodes	O
packaged	O
so	O
as	O
to	O
be	O
surrounded	O
by	O
a	O
conductive	O
electrolyte	O
and	O
gas	O
ingress	O
controlled	O
with	O
a	O
diffusion	O
limited	O
capillary	O
.	O
</s>
<s>
MEMS	B-Architecture
hydrogen	B-Algorithm
sensor	I-Algorithm
–	O
The	O
combination	O
of	O
nanotechnology	O
and	O
microelectromechanical	B-Architecture
systems	I-Architecture
(	O
MEMS	B-Architecture
)	O
technology	O
allows	O
the	O
production	O
of	O
a	O
hydrogen	B-Algorithm
microsensor	I-Algorithm
that	O
functions	O
properly	O
at	O
room	O
temperature	O
.	O
</s>
<s>
One	O
type	O
of	O
MEMS-based	O
hydrogen	B-Algorithm
sensor	I-Algorithm
is	O
coated	O
with	O
a	O
film	O
consisting	O
of	O
nanostructured	O
indium	O
oxide	O
(	O
In2O3	O
)	O
and	O
tin	O
oxide	O
(	O
SnO2	O
)	O
.	O
</s>
<s>
A	O
typical	O
configuration	O
for	O
mechanical	O
Pd-based	O
hydrogen	B-Algorithm
sensors	I-Algorithm
is	O
the	O
usage	O
of	O
a	O
free-standing	O
cantilever	O
that	O
is	O
coated	O
with	O
Pd	O
.	O
</s>
<s>
Pd-coated	O
nanomechanical	B-Algorithm
resonators	I-Algorithm
have	O
also	O
been	O
reported	O
in	O
literature	O
,	O
relying	O
on	O
the	O
stress-induced	O
mechanical	O
resonance	O
frequency	O
shift	O
caused	O
by	O
the	O
presence	O
of	O
H2	O
gas	O
.	O
</s>
<s>
Chemochromic	O
hydrogen	B-Algorithm
sensors	I-Algorithm
–	O
Reversible	O
and	O
irreversible	O
chemochromic	O
hydrogen	B-Algorithm
sensors	I-Algorithm
include	O
a	O
smart	O
pigment	O
paint	O
that	O
visually	O
identifies	O
hydrogen	O
leaks	O
by	O
a	O
change	O
in	O
color	O
.	O
</s>
<s>
Sensors	O
are	O
typically	O
calibrated	B-General_Concept
at	O
the	O
manufacturing	O
factory	O
and	O
are	O
valid	O
for	O
the	O
service	O
life	O
of	O
the	O
unit	O
.	O
</s>
<s>
Siloxane	O
enhances	O
the	O
sensitivity	O
and	O
reaction	O
time	O
of	O
hydrogen	B-Algorithm
sensors	I-Algorithm
.	O
</s>
