Geiger obviously measures side-effect from of the lethal scent-anomalies - Ultraviolet radiation.
- The lethal scent-anomaly can be present so that Geiger does not notice it.
- Geiger can incorrectly inform about the presence of lethal scent-anomaly.

When you know the source and the radiation grows, you are carrying lethal scent-anomaly with you. Meter can never separate anomalies from scent.

Since you are measuring side-effect, you can never be sure, how much lethal scent-anomaly you are carrying. An old almost fully radiated radiation suit can for example show marginal radiation levels.

One thing in light and ultraviolet light is, that the source of radiation can be far from the place, where you measure the side-effect from the lethal scent-anomaly.