At what relative humidity do MIL-I-26860 indicator plugs change color from blue to pink?

At what relative humidity do MIL-I-26860 indicator plugs change color from blue to pink?

• A. 5-15% relative humidity
• B. 20-30% relative humidity
• C. 35-45% relative humidity
• D. 60-70% relative humidity

Answer: (C)

Indicator plugs monitor the humidity inside a sealed package and provide a visible warning when moisture levels rise enough to risk damage to sensitive parts. They start blue when dry and shift to pink as humidity reaches their activation threshold. For MIL-I-26860, that activation point is set in the mid-range, roughly 35 to 45 percent relative humidity. So when the plug turns pink, it indicates the environment has reached moisture levels that could lead to moisture-related issues, signaling that drying or repackaging may be needed to maintain component integrity. If the humidity stayed well below this range, the plug would remain blue; if it were much higher (well above 45%), you’d expect it to be pink as well, but the specification is tuned to the 35–45% activation window for timely warning.

Indicator plugs monitor the humidity inside a sealed package and provide a visible warning when moisture levels rise enough to risk damage to sensitive parts. They start blue when dry and shift to pink as humidity reaches their activation threshold. For MIL-I-26860, that activation point is set in the mid-range, roughly 35 to 45 percent relative humidity. So when the plug turns pink, it indicates the environment has reached moisture levels that could lead to moisture-related issues, signaling that drying or repackaging may be needed to maintain component integrity. If the humidity stayed well below this range, the plug would remain blue; if it were much higher (well above 45%), you’d expect it to be pink as well, but the specification is tuned to the 35–45% activation window for timely warning.