AHAM vs Saturation PPD

AHAM PPD is measured at 80°F and 60% relative humidity. Saturation PPD is measured at higher temperature and humidity, typically 90°F and 90% RH. Crawl spaces are usually cooler (50-60°F), so actual water removal will be lower than both ratings.

AHAM PPD (Association of Home Appliance Manufacturers)

AHAM PPD is the standardized rating for dehumidifiers in the United States. Test conditions:

• Temperature: 80°F (26.7°C)
• Relative Humidity: 60%

This is the number you see in product names: "90 pint dehumidifier" means 90 pints per day at AHAM conditions.

Saturation PPD

Saturation PPD (also called "max PPD" or "saturation capacity") is measured at maximum load conditions:

• Temperature: Typically 90°F (32°C)
• Relative Humidity: 90%

At these extreme conditions, the dehumidifier removes more water per day. The AlorAir Sentinel HDi90, for example, removes 90 pints/day at AHAM conditions but 198 pints/day at saturation.

Why Both Numbers Matter

AHAM PPD is useful for comparing units on a standardized basis. All manufacturers must test at 80°F/60% RH for AHAM certification.

Saturation PPD shows peak capacity in extreme conditions (hot, humid summer). This is closer to what you might see in a flooded crawl space after heavy rain in warm weather.

What About Crawl Spaces?

Most crawl spaces are cooler than 80°F. Typical crawl space temperatures:

• Summer: 60-70°F
• Winter: 45-55°F (or colder in northern climates)

At lower temperatures, dehumidifier output decreases. A unit rated for 90 PPD at 80°F/60% RH might produce 65-75 PPD at 60°F/60% RH.

We do not invent "crawl space PPD" estimates. We report manufacturer AHAM ratings and note that crawl space output will be lower due to cooler temperatures.

Which Manufacturers Publish Saturation PPD?

*AprilAire publishes capacity at 73°F/60% RH (65 PPD for E080), not true saturation. This is not saturation PPD.

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