When I hover my cursor over a filter machine, the area it covers is highlighted. That is useful for knowing what the machine covers, but the highlight is much too bright, especially for the higher-level machines, whose coverage area is usually most or all of the screen. The instant the cursor touches a filter machine the entire screen lights up in an effect that is very much like, and can be confused with, the red flash when the character is taking damage. It's especially jarring when I am running around, with the mouse cursor idle on the screen near the character; if I run past a filter machine, the cursor hits the machine for a split second and the whole screen flashes.

I wish that this highlight could be made much dimmer, similar in intensity to the highlights used by power poles to show their coverage areas. Roboports are also a point for comparison: they use a fairly bright highlight, but still less than an air filter machine's highlight, and the roboport highlight fades in slowly instead of being an instant flash. I prefer the dim highlight like a power pole, but the fade-in does help. Even with a fade-in, I think the filter machine highlight is too bright.