Why does our porta potty smell like ammonia after a hot week?

The ammonia smell is from urine breaking down into ammonia gas, a process that speeds up dramatically in high heat. Your standard portable toilet is a closed system, and the holding tank heats up like an oven in Phoenix's summer sun. This heat accelerates the decomposition of urea in the urine. The deodorizer the service company uses is designed to control odors and slow this process, but it can be overwhelmed.

Weekly service visits are the industry standard for normal conditions. However, with 20 workers using a single unit daily in extreme heat, the service frequency is not enough. The unit is being used heavily, and the chemical is breaking down faster than it can work. You need more frequent service when it's this hot. The rental company should pump the waste, scrub the interior, and recharge the holding tank with fresh deodorizer more than once a week. The cost of the rental will increase with the added service trips, but it's the only way to control the odor in that environment.