Indoor air quality is a significant concern due to the potential health risks and comfort issues associated with air pollutants. This study aimed to assess the concentrations of nitrate, ammonium, and sulfate in indoor water-soluble particulates in the air of both medical and residential sites in Damietta, Egypt. Thirty-five samples of particulate matter were collected from 15 medical sites and 20 residential sites from May to August 2021 located in Damietta City (urban) and El- Basarta village (suburban). The results indicated that indoor air is influenced by high concentrations of NO₃^-, NH₄⁺, and SO₄^2-. The outdoor NO₃^-, NH₄⁺, and SO₄^2- concentrations were higher than indoor ones. It was observed that the concentrations of the determined parameters (NO₃^-, NH₄⁺, and SO₄^2-) were higher in the medical sites than the residential ones and also higher in the urban sites than the suburban ones. Additionally, the I/O ratios of NO₃^-, NH₄^+, and SO₄^2- in almost sites were below 1.0 indicating the relatively high influence of the outdoor sources on the indoor air. Therefore, it was recommended to use more natural cleaning materials to improve indoor air quality, and clean indoor spaces often by vacuuming or mopping to remove hazardous pollutants.