During regeneration, oxygen concentration is kept at what level to prevent burning?

• A. 2% to 4%
• B. 5% or more
• C. 1% or less
• D. 0%

Answer: (C)

Keeping oxygen very low during regeneration is about preventing any ignition of combustible materials that may be released or exposed as the process heats or reactivates the material. Oxygen fuels combustion, so creating an inert-like environment by limiting O2 to about 1% or less minimizes the risk of burning. While zero percent O2 would be ideal, in practice small leaks keep a tiny amount present, and 1% or less is the practical, safe threshold used. Higher oxygen levels, even a few percent, can create a flammable or explosive mix depending on temperatures and vapors involved, so they’re avoided during regeneration.