Fungus growth

We had kept few pulp drums in 8 deg cent. Temperature for a month and suddenly changed temperature to 25 deg cent. Then after 2 days we found fungus growth on drums sirface. How does it happen. Is it because of sudden temperature drop or any issue with cold storage room? Please help me.

Perhaps the relative humidity is too high…?You should try installing a dehumidifier in your cold storage area…

It can be cross-contamination from other products taken in and out of the room.

Most cardboard ( pulp) drums are moisture absorptive;so any goods stored in it should be stowed in low humidity environments preferably on cold temperatures. Another thing if it’s stowed just near the floors susceptible to moisture condensation it will gradually be absorbed by the cardboard creating an environment where fungus growth can initiate and proliferate Ordinary Cold rooms usually have higher humidity and having a sterile environment is a rarity.
If the storage temperature is suddenly changed from refrigeration temperature to ambient around 25 to 30C and high humidity it is inevitable that mold growth will rapidly manifest on those moisture absorbent material like cardboard drums.
The OP should bring the temperature down to previous values where this fungus problem did not occur.

What is your Enviornmental Micro count? Fungus and Mold are common in these storage conditions. Make sure you have proper air circulation and install uV lamps in the room. It will help in taking care of any enviornment microbial issues.