Abstract: Effect of air flow on cables combustion and flame shape in tests of flame spread, heat release, and smoke production of cables or optical fibers under fire conditions were investigated by adjusting air flow in combustion chamber. At the same time, advantages and disadvantages of common methods for measuring air flow in pipes were compared, combined with air volume equilibrium law, measurement accuracy and flow velocity distribution characteristics of air flow in combustion chamber were simulated by using air flow measurement method based on air volume hood. Results showed that stability of air flow into combustion chamber under different pipe layouts was quite different, this difference will be further increased due to inconsistent measurement position of air flow in pipeline, and air flow measurement method in combustion chamber based on air volume hood could accurately and conveniently address the issue of inconsistent measurement locations in duct airflow measurement, and provide effective technical guidance for pipe layout of circular pipe before combustion chamber in GB/T 31248—2014.