To those who live in areas where there are plenty of water, like those near the equator, humidity is very high. Camera lenses, if are not kept carefully, in no time mold will grow on the glass surface. Even if you keep it in an airtight box/container together with desiccant. The mold will still be present on the glass if you do not maintain the condition of the desiccant by reheating it every so often to remove the moisture. I know, I have been there and done that. If the mold is on the surface of the external lens, and after you clean the lens to remove it you will find that your lens coating is partly gone too. The lens can still be used only that it does not look good anymore. I have been using the method that I am about to explain for almost two years and not a single thread of mold on the lenses even though I have been out in a light rain and my lenses are not weather sealed.
What you need is a box/container that will take in all your gears, a 5 watt incandescent bulb, bulb holder, light dimmer, a length of electrical cord and a plug. Install the bulb holder on the lower part of the box and connect it to the light dimmer and plug. Leave some space for the bulb by putting something to act as raisers perhaps small block of woods on all four corners and cover it. The cover should be something solid that will take the weight of whatever that will be on it. Make sure there is space for the warm air to rise to the above compartment or drill some holes in the cover. If you wish, you may drill a very small hole at the bottom of the box/container to let cold air out and as a precaution not to pressurised the box/container.
Note of caution: If you don’t know anything about electrical wiring, get someone who knows to do it for you. Never attempt to do it if you have no clue about electrical wiring. Electric shock can be fatal and electrical wiring short can cause fire.
That said, here’s how I did mine. I have a commercial dehumidifier dry box that is not working anymore, even the gauge. Looking at it, I have a hard time figuring how the system work. So I remove the whole dehumidifying system and in its place I install a 5 watt incandescent bulb and a light dimmer so that I can control the amount of heat generated. Not too warm (detrimental effect for the electronics inside the lens and camera if exposed for a very long period) or warm but just a slight feeling of warmness in the air and since the bulb is working underrated, it last a very long while.