Why does our porta potty smell worse after the service visit?

That harsh cleaner smell right after a service visit is usually normal when the tech just charged a freshly pumped holding tank.

On our jobs the unit smells sharp for a few hours after the weekly pump-out because the blue liquid sits concentrated until waste and rinse water dilute it. Your driver pumped, put in the charge, and restocked paper, so the stop itself sounds complete. What you are smelling is the fresh deodorizer, not leftover waste.

If it still burns your nose the next morning, ask whether they used a different formula or poured a heavier dose than usual. Cracking the door for a few minutes after service helps the plastic cabin air out. Waste odor coming back later in the week is a different problem (tank getting full or a thin charge). Fresh chemical punch right after service is the common pattern on a standard unit with a Tuesday stop.

Carl is correct about the concentrated deodorizer causing the initial smell, but the harsh chemical odor can also indicate a formaldehyde-based formula. Most rental companies now use formaldehyde-free deodorizer to meet wastewater treatment plant disposal rules, as formaldehyde is restricted. If the smell is unusually strong and lingers, the driver may have added the standard charge to a completely empty holding tank without the usual initial waste dilution. A quick call to the rental company can confirm their chemical type. For your crew size, OSHA 1926.51 requires only one toilet, so your single unit is sufficient and weekly service is appropriate.