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[fralexandr]

http://support.brother-usa.com/Mode...0_7040_MFC_7340_7345N_7440N_7840W_EN_6998.PDF
machine
operating temp 10 to 32.5C
storage temp -20 to 40C

consumables
storage (normal) 0 to 40C
storage (<5 days) @ 40 to 50C
storage (<5 days) -20C to 0C

pdf also has humidity info

toner is already a dry powder
http://en.wikipedia.org/wiki/Toner

 

[tidy]

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[corkyg]

My own experience says that high humidity is more likely to lead to caking. If the environment is hot and humid, it would not be a bad idea to pull the toner cart and give it a good shake now and then.