Whether the mobile phone waterproof bag can prevent steam depends on the material. Most mobile phone waterproof bags on a treasure (the price is lower than 60) can't prevent steam, because they are made of PVC with a melting point of 50-60 degrees. 

How can they withstand a high temperature of 80-100 degrees? In contrast, TPU mobile phone waterproof bags, such as podragon mobile phone waterproof bags, did not drop the chain in the high-temperature test. After many hot springs and long-term use, the sealing is reliable and practical.

A good waterproof bag for mobile phone can withstand high temperature and cold. Use waterproof cell phones in bathrooms. Of course, you need to learn more about waterproof cell phones in some places.