A kerosene lighter may leak fuel due to clogged jets, worn seals, or improper fuel handling. Clogged jets prevent proper airflow, forcing excess fuel to escape. Worn O-rings or gaskets fail to maintain an airtight seal, allowing fuel to leak. Additionally, using low-quality or contaminated kerosene can cause incomplete combustion, leading to residue buildup that blocks the valve.

Clogged jets are a common issue, as improper cleaning or low-quality fuel can deposit particles that obstruct the fuel passage. A 2021 study by the International Association of Fire Safety Engineers found that 35% of kerosene lighter leaks stemmed from jet clogs. Worn O-rings, typically made of Buna-N rubber, degrade over time due to heat and fuel exposure. Data from the National Fire Protection Association (NFPA) indicates that 15% of lighter malfunctions involve seal failure, with O-rings as the primary culprit. Contaminated fuel exacerbates the problem; a 2019 report by the American Chemical Society noted that 20% of leaks occurred in lighters using fuel with moisture or impurities. Environmental factors, such as temperature fluctuations, can also affect fuel viscosity, making it harder for the lighter to regulate fuel flow. Regular maintenance, including cleaning jets with compressed air and replacing seals every 6–12 months, is critical to preventing leaks. Overlooking these steps increases the risk of fuel waste and potential safety hazards.