Background: Chronic exposure to biofuel smoke is a major risk factor for respiratory impairment in developing countries, yet its impact on ventilatory function and the role of exposure duration remain understudied in Northeast Nigeria. Objective: The study aimed to evaluate ventilatory function parameters and the effect of exposure duration on lung function among commercial food vendors exposed to biofuel smoke in Maiduguri, Nigeria, compared to controls. Methods: A cross-sectional study was conducted involving 182 food vendors using biofuels and 185 age-, sex-, and height-matched controls. Spirometry measured peak expiratory flow (PEF), forced expiratory volume in 1 second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio. Ventilatory defects (obstructive/restrictive) were defined using Global Lung Function Initiative Lower Limit of Normal criteria (LLN). Exposure duration was assessed via questionnaire. Groups were compared using t-tests and chi-square tests, with Pearson’s correlation for exposure duration and lung function, at p<0.05. Results: Vendors exhibited significantly lower PEF (5.95 ± 1.17 vs. 6.49 ± 1.12 L/s, p<0.001), FEV1 (2.39 ± 0.49 vs. 2.65 ± 0.49 L, p<0.001), FVC (3.10 ± 0.49 vs. 3.39 ± 0.54 L, p<0.001), and FEV1/FVC (76.72 ± 5.44% vs. 78.30 ± 4.26%, p=0.002) than controls. Obstructive defects were observed in 8.2% of vendors vs. 4.3% of controls (p=0.13); restrictive defects in 1.6% vs. 0.5% (p=0.34). Exposure duration negatively correlated with FEV1/FVC (r=-0.23, p=0.002). Conclusion: Biofuel smoke exposure impairs ventilatory function, with longer exposure exacerbating airflow limitation, highlighting the need for occupational health interventions in Nigeria.