Content check portable oxygen device (stroller): After filling the stroller one can check the content of the stroller, it depends the model provided how to go about this. Certain strollers have an indicator with LED lights but often one has to pick up the stroller and hold it by the shoulder strap. Between the shoulder strap and the device a small measuring scale is located. The weight of the stroller is indicated on the scale. If the indicator is showing the green part the stroller will contain sufficient oxygen, if the indicator is red it needs to be filled more. In case the stroller has a led light indicator make sure that the batteries are working.