Previous studies have reported increased occurrence of respiratory and sensory irritation symptoms among residents living close to biodegradable waste sites. However, few studies have been able to quantify direct and annoyance-mediated effects based on individual-specific assessments of chemical exposures. We examined associations between residential exposures to a proxy gas (ammonia, NH3) from biodegradable wastes (mainly from farming, animal and agricultural activities) and odor annoyance and six respiratory and sensory irritation symptoms (self-reported), using adjusted logistic regression models and mediation analyses. Individual-specific NH3 exposures (n = 454) in residential environments during 2005-2010 were calculated by the Danish Eulerian long-range transport model and the local-scale transport deposition model. Residential NH3 exposure was associated with increased frequency of four symptoms, including “eyes itching, dryness or irritation” and “cough” (ORadj = 1.69; 95% CI: 1.09-2.61 and ORadj = 1.75; 95% CI: 1.12-2.74, for each unit increase in loge(NH3 exposure)). Odor annoyance mediated the effect of exposure on cough and three sensory irritation symptoms. Mediation was either full (indirect-only effects) or partial (direct and indirect effects). This study provides support for the existence of indirect associations between residential exposures to low-to-moderate air pollution from wastes and symptoms, as well as direct dose-response associations for some of the symptoms.