GPP, dew point and grain depression. Compare air conditions and record each drying day—free, without an account.
Enter temperature and RH to calculate each reading.
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Elevation: 0 ft · Temperature: °F
| Location | Temp °F | RH % | GPP | Dew point °F | Vapor inHg |
|---|---|---|---|---|---|
| Outside | — | — | — | ||
| Unaffected area | — | — | — | ||
| Affected area: Chamber 1 | — | — | — | ||
| Dehumidifier 1 inlet | — | — | — | ||
| Dehumidifier 1 outlet | — | — | — |
Enter temperature and RH to calculate each reading.
The readings that matter
GPP is grains of water vapor per pound of dry air. Unlike RH, it lets you compare moisture content at different temperatures. Heating air can lower its RH without removing water. A falling GPP trend shows air is getting drier, but material moisture readings are still needed to assess the structure.
Dew point is the temperature at which the measured air becomes saturated. Water can condense on surfaces at or below that temperature; below freezing, ice or frost may form. Compare it with cold surface temperatures when assessing condensation risk.
Subtract outlet GPP from inlet GPP to see how much moisture a dehumidifier removes per pound of air passing through it. Compare the same unit across visits under similar conditions. This is not gallons per day: airflow and operating conditions also affect total removal.
Temperature increases from left to right; GPP increases upward. Curves mark 10% through 100% RH. Each dot is a reading. An inlet-to-outlet arrow moving downward shows moisture removal. Two days or more reveal a GPP trend for each location.
At sea level, inlet air at 90°F / 60% RH contains 127.9 GPP. Outlet air at 95°F / 25% RH contains 61.3 GPP. The unit removes about 67 grains of moisture per pound of dry air (66.6 to one decimal)—even though the outlet is warmer.
Take readings at least on each monitoring visit and after meaningful equipment or condition changes, following your company’s procedures. Record date and time, technician, chamber and unit names, air temperature and RH, material moisture at repeatable points, equipment changes and site conditions. Air readings alone do not establish that materials are dry.
GPP measures the weight of water vapor per pound of dry air. RH describes how close air is to saturation at its current temperature. Warm air can have lower RH but still contain more moisture; compare GPP when temperatures differ.
Yes. Atmospheric pressure falls as elevation rises, so the same temperature and RH produce a higher humidity ratio and GPP. Dew point and vapor pressure stay the same. The elevation setting uses standard-atmosphere pressure, not measured local barometric pressure.
Yes. Select °C to enter Celsius temperatures and view Celsius dew points. Existing temperatures are converted when you switch units. The psychrometric chart retains its labeled Fahrenheit axis.
Outside air with lower GPP can reduce indoor air moisture when introduced safely. Higher-GPP air can add moisture. Temperature, contamination, containment and your drying plan also matter; a GPP comparison alone is not permission to ventilate.
LGR units condense water using refrigeration and perform within a temperature and humidity operating range. Desiccant units use a moisture-absorbing material and often remain useful at lower temperatures or humidity. Compare performance with the manufacturer's rating for the actual conditions; grain depression alone is not a capacity measurement.
Yes. Print / Save as PDF produces the log tables and charts for every day. Download CSV exports readings and grain depression. The log saves in this browser only and is not imported into RestorationWorkflow job records.
In RestorationWorkflow, environmental readings live on the job record and are pulled into the report draft, and built-in calculators size dehumidifiers and air movers from your inspection data.
Calculations use standard psychrometric formulas at the pressure for your elevation. Readings and drying decisions remain your professional responsibility; follow your company's procedures and the standards that apply to your jobs.
