Humidity

Relative humidity is the measurement of water vapor in the air. In general, deep desert species do well with ambient humidity in the 40% to 60% range. Even lower is acceptable if suitable moist shelters/burrows are present. Tropical species require higher humidity from 75% to 90%. Intermediate species will require levels in between. Maintaining proper humidity levels can be done easily by choosing proper substrate, controlling ventilation, and regular misting.

Misting with room temperature water is by far the most common and simplest way to increase cage humidity. I would recommend spraying desert species lightly twice per week, and rain forest dwellers as much as twice per day. Experimentation and the use of a quality humidity gauge will help you to determine the proper misting schedule for your specific set-up. You can use bottled water, or distilled water for cage misting. Tap water leaves ugly water spots and mineral deposits on the walls of your enclosure.

If humidity is too high then cease introducing any water for a period of time (possibly days) until the level has come down. No enclosure should ever be 100% humidity. This would be too wet, encourage mold and kill the spider. Keep in mind 45% to 55% is the optimum relative humidity range to reduce promotion of growth in bacteria, fungi and mites.

Sources:

Optimum Relative Humidity Ranges for Healthier Indoor Air, Theodore D. Stirling and Associates, Canada: http://www.gasairconditioning.org/relative_humidity_chart.htm

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