Model 221R
The Model 221R has become the standard oxygen
deficiency monitor throughout the US market. It is used by the
thousands in government labs, universities, and industry, anywhere there
is a possibility of asphyxiation due to leakage of compressed or
liquefied inert gases like nitrogen, argon or carbon dioxide.
It has become the standard because it is extremely
reliable, does not drift even with extreme temperature swings or
barometric pressure changes and does not generate false alarms but
responds very rapidly to real oxygen emergencies.
Competitive monitors that use conventional
electrochemical sensors suffer from serious false alarms issues.
Electrochemical sensors lose sensitivity over time – requiring monthly
calibration - and typically after about a year need to be replaced.
These sensors suffer from pressure and temperature sensitivities that
cause them to drift into alarm when weather patterns change or even when
air conditioning systems cycle, even though the actual oxygen level is
safe.
The model 221R offers a number of compelling features
that make integration into building or plant alarm systems easy.
It provides two alarm relays, operating in fail-safe
mode that provide up to 110V at 5A switching capability. They respond
to the standard OSHA alarm levels of 20.0% warning, 19.5% danger, and
they also respond to a 23.5% over-enrichment situation.
The front panel status LED changes color when an
alarm occurs, and when a danger alarm occurs the built-in audible alert
sounds. This alarm can be temporarily silenced.
It can be calibrated using a known clean air sample,
but it only needs calibration bi-annually, and then mainly in order to
verify its calibration.
It provides an isolated 4-20mA output corresponding
to the oxygen reading that can be monitored by an analog control panel.
It provides a bi-directional RS-485 communication
system that can monitor all the internal parameters and even download a
data log of readings over the previous fifteen days.
It can be mounted on a wall, and hosed down. It is
available with a remotely mounted oxygen probe, so that the display and
alarm can be seen outside a room while the air within the room is
monitored, so personnel may be kept out when conditions are dangerous.
It contains enough batteries to allow it to continue
operating up to an hour after power failure, and it will indicate an
alarm for a period before the batteries completely die.
