Formaldehyde-free deodorizer: does it work as well in heat?

I'm managing a construction site with 30 workers, and we've had our standard portable toilets for about six weeks now. The rental company services them weekly, but by the third day in this 90-degree heat, the odor is noticeable even from a distance. We're considering switching to a formaldehyde-free deodorizer for environmental reasons, but I'm worried it won't hold up as well in high temperatures. Has anyone made the switch during summer? Does the eco-friendly option keep odors under control just as effectively, or do you end up needing more frequent service visits?