Carbon Monoxide Detectors

4 years ago we had a new gas boiler fitted outside in the garage instead of in the house in the boiler room as it had been previously.I then decided that the Co2 detector was of no use in the house and so fitted it in the caravan.My daughter has now had the van for 3 years and has had it serviced annually,but last week she had it serviced by a mobile fitter who said that the detector was not of caravan specification.I didn't know there was a difference Any thoughts on this.