Combustion Modified Excelsior contains an additive to reduce its flammability around ignition sources, however like most fiberous materials, you should not expose to open flame or heat sources. Over time, the effectiveness of the additive may be reduced by direct sunlight and/or watering, so you should replace the material from time to time, depending on the amount of exposure to these factors. For questions about its use, contact our Customer Service Dept at 800-777-7645.