BACKGROUND AND AIM: Household air pollution (HAP) is associated with adverse human health impacts. During COVID-19 Hard Lockdown Level 5, South Africans remained at home, potentially increasing their exposure risk to HAP. This study was conducted to investigate changes in fuel use behaviours / patterns affecting HAP exposure and associated HAP-related health outcomes during the COVID-19 Hard Lockdown that started 23 March, 2020. METHODS: This was a cross-sectional online and telephonic survey of participants from an existing database. HAP exposure indicators were considered before and during Hard Lockdown. Participants were also asked about HAP and COVID-19 symptoms/tests before and during this lockdown. Logistic regression and McNemar’s test were used to analyse household-level data. RESULTS:Among 2,505 participants, while electricity was the main energy source for cooking and heating before and during Hard Lockdown, some households used less electricity during Hard Lockdown. A majority of households reported cooking more, cleaning more, and spending more time indoors during the lockdown. Age (older), gender (male), and number of people (an increase) living in the dwelling affected the presence of HAP-related health outcomes. For fuel type used for heating, paraffin had the highest significant odds ratio (1.89 p = 0.015, CI 1.13 - 3.16) compared to electricity (applied as reference category) as the heating fuel type used in a household that reported COVID-19-related health symptoms and / or confirmed COVID-19 cases (combined analysis). CONCLUSIONS:This study showed that increased number of people living in a dwelling and using paraffin for heating increased the odds of those households having HAP-related health outcomes. Several of these are similar to COVID-19 symptoms. Should South Africa return to Hard Lockdown Level 5, awareness raising about the risks associated with HAP as well as messaging information for prevention of exposure to HAP and adverse health impacts will be necessary to inform the public. KEYWORDS: dirty fuels, environmental health, fuel patterns, household air quality, respiratory health