Hi Ron, at risk of declaring the length of my teeth can I just say that during my time off shore in the north sea and other god forsaken holes around the world we used a lot of IR detection not so much UV. The problem we found was with the unwanted response to solar and other spurious UV generating processes and the lack of response to the products of combustion we wanted to detect, however modern combined UV and single frequency IR detectors are far better at rejection of these phenomena.
One thing is important and I think this is why the client is asking for the performance test he is, is that the particular liquids ethanol or methanol have different properties vis products of combustion when burned and the client would need to be assured that his particular risk was being mitigated. I assume that by carrying out a fire test using this product which was successfully detected by the IR/UV detector he would be satisfied.
Be careful though if attempting this it must be done under controlled conditions.