Spectrex 40/40M Multi IR Flame Detector - Manual (Page 22)

Multi IR Hydrocarbon and Hydrogen Flame Detector User Guide
10 Performance Considerations
Figure 2: Horizontal Field of View for Gasoline
1.5.2.2 Hydrogen
 Horizontal: 80°
 Vertical: 80°
Figure 3: Fields of View for Hydrogen (Horizontal and Vertical)