What is OIML Class 1?
This is the defining standard for exhaust monitoring equipment accuracy, performance and functionality across Europe. All MOT Test Station analyser must meet this standard.
The critical parameters are as follows:
| Feature | Range | Resolution | Accuracy | |
| vol | % | |||
| Oxygen | 21% | 0.02 | + 0.1% | + 5% |
| Hydrocarbons | 2000 ppm | 1 | + 12ppm | + 5% |
| Carbon Monoxide | 5% | 0.01 | + 0.06% | + 5% |
| Carbon Dioxide | 16% | 0.1 | + 0.5% | + 5% |
| Oil Temperature | 150°C | 1 | + 2.5°C | |
| Tachometer | 5000 rpm | 1 | + 0.5% | |
These measurements must be correct for a range of ambient temperatures, humidities and atmospheric pressures.
Please note that NOx measurements are currently not within the scope of the OIML criteria.