To safely trim the cotton core in a kerosene lighter, first ensure the lighter is completely off and cooled. Use clean, sharp scissors or a utility knife to carefully cut the wick 1/8 inch (3 mm) above the fuel chamber. Avoid trimming while the lighter is lit or when fuel remains in the tank. Reinsert the wick and test the lighter to confirm proper ignition.

Proper cotton core trimming is critical for safety and efficiency. A wick that is too long can cause uneven fuel distribution, leading to excessive fuel consumption and potential dripping, while a wick that is too short may fail to ignite reliably. According to a 2021 study by the National Fire Protection Association (NFPA), improper maintenance of lighters contributed to 12% of outdoor fire incidents in the U.S. that year. Additionally, a 2019 analysis by the Journal of Fuel Technology found that wicks exceeding 1/8 inch resulted in 20-30% more fuel waste due to incomplete combustion. Trimming the core to the recommended length ensures optimal fuel-to-air ratio, reducing fire hazards and extending lighter lifespan. The NFPA also emphasizes that 70% of lighter-related accidents involve misadjusted wicks, underscoring the need for precise maintenance. By adhering to these guidelines, users minimize risks and enhance operational performance.