– 23 –
Monthly check: Concentration controller
Set the concentration to 50% n
2
o and set any flow. the
o
2
and n
2
o bars in the bottom right should soon equal-
ise. now set the concentration to 0% n
2
o. the n
2
o bar
should drop and only the o
2
bar should be visible after
a short period of time. you can perform the check dur-
ing each treatment when you ventilate the patient with
100% o
2
at the end.
Monthly check: Check n
2
o
Set the concentration to 50% n
2
o and set any flow. now
close the n
2
o cylinder. the n
2
o bar should drop and the
unit should signal “Check n
2
o” visually and acoustically
after a short period of time.
Monthly check: o
2
Flush
Press the o
2
flush button. the breathing bag should in-
flate within five seconds and the “flush” information sig-
nal should appear in the display.
after each treatment with nitrous oxide
and oxygen: Venting the nitrous oxide
system
1. the nitrous oxide and oxygen cylinders are open after
the treatment.
2. Close the nitrous oxide cylinder.
3. Set the maximum n
2
o concentration and any total flow.
4. the n
2
o bar gets smaller and only the o
2
bar is visible
after a short period of time. the nitrous oxide is now
vented and there is no more nitrous oxide in the ni-
trous oxide system. the “Check n2o” information sig-
nal appears.
5. now close the oxygen cylinder.
6. the “Check o
2
” information signal appears after a short
period of time.
7. the system is vented. Both pressure reducers now
show 0 bar.
8. you can now switch off the unit and loosen the pres-
sure reducers and pressure hoses by hand if you wish.
6.5 ambient air contamination
nitrous oxide occupational exposure limit
value as per tRGS 900
German nitrous oxide occupational exposure limit value:
100 ppm for nitrous oxide treatments lasting 30 minutes
or longer. the occupational exposure limit value may be
exceeded by a factor of 2 for a treatment duration of e.g.
15 minutes (200 ppm).
exposure time (min.)
15
20
25
30
exceedance factor
2
1.5
1.2
1
the occupational exposure limit value defines the nitrous
oxide concentration at which acute or chronic damaging
effects to general health are not expected (Section 3 (6)
of the ordinance on Hazardous Substances [GefStoffV]).
occupational exposure limit values are time-weighted
averages for usually eight hours of exposure daily on five
days of the week during a working life.
the limit values differ from country to country and are
the subject of discussion. the operator is responsible for
complying with concentration limits for nitrous oxide in
the ambient air.
nitrous oxide exposure should be kept as low as possi-
ble to protect staff. the following aspects should be ob-
served for compliance with the trGS 900 occupational
exposure limit values:
(refer to the table on the next page)
