Land hermit crabs breathe through a modified gill. It is important to protect the gills from strong fragrances, essential oils, candles, household cleaners, chemicals, smoke insecticides and other airborne irritants.
Be mindful of what you spray or use near the crabitat even if your tank is fully sealed. Residual product may still be in the air when you open your tank.
If you are forced to have your home sprayed for insects ensure your tank is fully sealed with saran wrap or something similar. Allow the house to air out at least 24 hours before unsealing your tank.