Yes I mean the tubing that came with the fogger. PVC will serve you well!
Maybe you should start misting for longer sessions, or simply throwing in more sessions.
However... lets check something else out first.
How close is your hygrometer to where your chameleon sleeps? IMO, you should have one RIGHT where he sleeps. As close as possible.
If I am seeing this right in this pic you provided, I am seeing your hygrometer near the top of the enclosure. Is this where he sleeps? If he sleeps elsewhere, I suggest adding another hygrometer to that location specifically....
Because with your schedule and running the fogger continuously I feel there's no way your humidity is that "low".
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However, if your fogger is running on say the opposite side of the enclosure, that makes perfect sense that your hygrometer is getting lower readings. And it's quite possible your readings are good (where he's sleeping). When you get a chance, let me know what's going on with this. In my enclosure, I have 3 hygrometers placed in different areas and they will all have different readings from each other because they're not all near where the fogging takes place.
Although 3 of your walls are solid (my enclosure is completely screen), the fog is just gonna likely fall in 1 direction. I am also willing to bet your chameleon is finding the best places for him to be hydrated at night.