Portable N
2
O Source Manual Rev. B-2
5
Description
Nitrous oxide is supplied to the instrument by means of N
2
O cartridges. Each
cartridge contains ~16 g or~ 8 g of liquid N
2
O. When using the Portable N
2
O Source
with the Model 211 Scrubberless Ozone Monitor, the cartridges will supply a gas flow
of N
2
O of 13 mL/min for ~8 hours (16-g cartridge) or 4 hours (8-g cartridge). For the
Model 408 NO Calibration Source, the cartridges will supply a gas flow of N
2
O of 40-
60 mL/min and provide an operating time of ~2 hours (16-g cartridge) or ~1 hour (8-g
cartridge). The pressure inside the cartridge remains nearly constant as N
2
O
evaporates and flows out of the cartridge. The evaporation of N
2
O causes the N
2
O
cartridge to cool, which, in turn, slightly reduces the internal pressure of ~600 psi.
Installation of N
2
O Cartridges
1) Make sure that any cartridge already installed in the assembly is empty by
checking that the reading on the pressure gauge is below 50 psi with the on/off
valve open. To make sure the valve is open, check that the knob cannot be
turned clockwise any further. Do not tighten the knob more than hand-tight.
2) Close the on/off valve by rotating the knob clockwise until you feel the knob
stop turning.
3) Unscrew the cartridge cup from the assembly. Do not completely remove the
cartridge cup until you are certain that any residual N
2
O gas has escaped. If
you hear a hissing sound, N
2
O is escaping. Once all the N
2
O has been vented,
completely remove the cartridge cup and remove the empty cartridge. The
cartridges are made of steel and may be recycled.
4) Insert a new cartridge into the cartridge cup with the narrow neck of the
cartridge pointed upward.
If using an 8-g N
2
O cartridge, the removable insert should be left in place in
the bottom of the black cartridge holder. If using a 16-g cartridge, slide the
insert out of the black cartridge holder.
5) Reattach the cartridge cup to the piercing device. As you screw the cup onto
the piercing device, the cartridge seal will be punctured, and as you continue to
Warning:
If an N
2
O cartridge is punctured outside the piercing
device/regulator, liquid N
2
O can escape, and if it evaporates on skin it will
cause frost bite. The cartridge will also act as a “rocket” if the seal is
punctured outside the piercing device/regulator. However, the N
2
O
cartridges are commonly used consumer products available commercially
and are safe to handle if the procedure below is followed.
