GE iVent 201 Series User's Reference Manual page 187

Cooling Air inlet filter
Battery
Ventilator
Every 2 years O2 sensor
Every 15000 hours or Pneumatic Assembly
every 4 years,
whichever is first
7 Care, Maintenance and Tests
Replace Cooling Air
inlet filter
Replace Battery
Perform full
calibration
It is good practice to
perform O2
calibration every 3
months.
Perform VVT
Perform safety
checks
Replace listed parts
by an authorized
VersaMed Service
Technician
Replace the O2
sensor
Replace parts by
authorized
VersaMed Service
Technician
175