Preventing Housing Lens Fogging

Canon housings are very compact and offer little room for heat generated by the camera. In order to prevent the interior housing lens and the camera's lens from fogging during a dive silica (dessicant) can be inserted into the housing into any available space. The dessicant packs shown below are color coded so as to be able to determine when they need replacement. They change from dark blue to pink when expired. These are two gram packets and easily fit in the G series camera housings as well as others. They can be purchased from the Preservation Station (http://preservesmart.com/products.htm#SilicaGelDesiccants). The company also sells loose re-chargeable dessicant should your housing have space for a larger amount.

In addition to the dessicant packets you can place cut-to-fit pieces of feminine panty liners into available spaces in the housing. They may save your camera should a small leak occur. The below photo shows a dessicant packet inserted into a G11/12 housing along with a section of a panty liner.
The below photo shows a additional section of a panty liner on the side of the housing. There is still room for a second dessicant packet between the pad and the black lens boot.
The below photo shows another section of panty liner in the bottom of the housing along with a section of a business card to indicate the owner's name and phone number should the housing be lost. There is always a possibility the finder will return it.
An additional way to prevent housing lens fogging is to turn the camera's monitor off while swimming and only turn it on when ready to take a photo. The monitor and the flash generate additional heat.