1. Measurement Equipment

2. Intrusive Observation
Efforts should focus on areas where there are signs of liquid moisture or water vapor (humidity), or where moisture problems are suspected.

3. Moisture Meters
Moisture meters measure/monitor moisture levels in building materials, and may be helpful for measuring the moisture content in a variety of building materials following water damage.
They also can be used to monitor the progress of drying damaged materials. These direct reading devices have a thin probe that is inserted into the material to be tested or pressed directly against the surface of the material.

4. Moisture Meters
Moisture meters can be used on materials such as carpet, wallboard, wood, brick, and concrete.

5. Moisture Content
Moisture content in wood is compared to the dry weight of the wood (called the Equilibrium Moisture Content (EMC). Wood (depending on type) becomes damp when the EMC exceeds about 18-20%. Mold is typically suspected if EMC is >17%

6. Moisture Content
Drywall and plaster with a moisture meter reading (drywall or plaster setting) >70-90% is considered damp and likely to support mold growth.
Plaster is typically much less sensitive to moisture and dampness than is standard paper backed drywall.

7. Hygrometer
A hygrometer is an instrument used for measuring the moisture content in the atmosphere. Humidity measurement instruments usually rely on measurements of some other quantity such as temperature, pressure, mass or a mechanical or electrical change in a substance as moisture is absorbed. By calibration and calculation, these measured quantities can lead to a measurement of humidity

8. Hygrometer

9. Humidity Gauges
Humidity meters can be used to monitor indoor humidity. Inexpensive (less than $50) models that monitor both temperature and humidity are available.

10. Humidistat
A humidistat is a control device that can be connected to an HVAC system and adjusted so that if the humidity level rises above a set point, the HVAC system will automatically turn on and reduce the humidity below the established point.

12. Boroscope
A boroscope is a hand-held tool that allows users to see potential mold problems inside walls, ceiling plenums, crawl spaces, and other tight areas. It consists of a video camera on the end of a flexible "snake." No major drilling or cutting of dry wall is required.

13. Boroscope

15. Ventilation Meters

16. Thermal Imaging Cameras

17. Data-logging
Battery-powered monitoring devices used to monitoring indoor air quality including temperature and relative humidity, VOC’s, ventilation rates and detecting hidden operating and maintenance problems.
Takes readings of the variables it is tracking and records for further evaluation.
Allows for a detailed diagnostic assessment of conditions which may impact occupants and mechanical building systems.

18. Data-logging

19. Precautions
Investigating hidden mold problems may be difficult and will require caution when the investigation involves disturbing potential sites of mold growth.
Dead mold may still cause allergic reactions in some people, so it is not enough to simply kill the mold, it must also be removed.