Gas phase nitrous acid (HONO) was measured from multiple platforms (insitu and remote sensing) in different urban environments (urban, industrical, near roadway, and suburban) as part of the 2009 Study of Houston Atmospheric Radical Precursors (SHARP) campaign. Data analysis and multi-scale modeling approaches have been used to access the importance of various HONO sources and to access the importance of HONO on Houston air quality. Multipath DOAS measurements indicate detectable gradients of HONO in both night- and daytime conditions. Zero-dimensional photochemical box modeling results indicate the importance of HONO as the primary early morning OH radical source and highlight the lack of sufficient HONO production capabilities of several different chemical mechanisms. One-dimensional box modeling suggests the importance of HONO emissions from a near surface source in both day and nightime hours. Analysis of the 1-D box modeling also indicates a strong near surface photochemical HONO source is required to maintain both the observed daytime HONO mixing ratios and the observed HONO gradient. The potential daytime HONO sources and the impact of HONO on photochemical ozone production in Houston will be further investigated in this presentation.