Can a catalytic bead sensor cause combustion?

NO.
A catalytic combustion gas sensor installed in a certified intrinsically safe instrument will not cause combustion or flame propagation, or excessive heat, for any reason when used in accordance with its design and ratings. Combustion caused by a catalytic bead sensor is, typically, only possible if the sensor has a compromised flame arrestor. The flame arrestor’s job is to prevent any flame, or sufficient heat, generated by the catalytic bead from reaching the detection environment where there could be flammable vapors and gases. As long as the instrument or detector head is rated and/or has the appropriate certifications, there’s no problem. Again, the flame arrestor prevents any potential flames, or enough heat, from getting to the detection environment. The flame arrestor’s surface, itself, also does not get hot enough to cause an issue. Catalytic bead sensors have been a safe and reliable technology for detecting a wide array of combustible gases and have been used for many, many decades.