Why does our unit smell like ammonia after a few days in the sun?

That ammonia smell is the deodorizer breaking down in the heat. The blue liquid in your standard portable toilet contains chemicals that release ammonia as they degrade, especially under direct sun and high temperatures like Phoenix summer. The holding tank acts like an oven, accelerating the process. It's not just waste odor, it's the deodorizer itself turning sharp and chemical.

Your crew of 25 has one unit, which meets OSHA 1926.51 for 20 to 199 workers (one toilet per 40). But with heavy use and heat, weekly service isn't enough. The unit fills faster, and the deodorizer burns off by Tuesday. Ask your rental company for a formaldehyde-free formula, they're less prone to ammonia breakdown. Also request twice-weekly service during hot months. More frequent pumping keeps the tank from overheating and the chemicals stable. Place the unit in shade if possible; even a few hours less sun helps.