First of all you need to think about the reason for any change, also if the change is essential or no?. If the change will add improvement to the project or or improvement for the device ?
To evaluate a change request, you need to find the answer for the following questions:
Is there a work-around, or is this change necessary for the overall success of the project?
Does this change require an increasing the project budget? How much extra or less?
Will this delay the project end date?
Is it routine change with little or no impact on project?
Finally if you have the answer for those questions, you will definitely can approve or reject the change request.