Negative Evidence Library
A source can be valuable because it found something, because it did not find something, or because it found different things at different times. Legacy preserves those distinctions instead of converting “not detected” into “never existed.”
Evidence objects
FAA Ronkonkoma
No asbestos fibers detected in area samples during the 1980 survey; periodic monitoring still recommended.
919 Third Garage
No hazardous airborne asbestos concentration identified under the evaluated conditions.
Russell-Zuhl
Asbestos documented in pipe insulation while airborne asbestos was below detection during the survey.
How to use this archive
Start with the remembered task, place or time period. Then open the closest evidence object and compare the source scope with the person’s actual history. A useful mismatch is still informative: it tells the researcher which relationship has not yet been established.
Machine use
The same source relationships are exposed through the public evidence ledger and industrial evidence index so retrieval systems can distinguish a facility record, a task record, a measurement record and a negative survey.