I have an S.M.C. industrial ceiling fan of type k56 (56''). It has a 5 speed control, but even on the lowest speed the fan runs far too fast. You do not feel comfortable at all in the room when it is running. I need to further reduce the speed.

There are speed controls for ceiling fans at a reasonable price at the DIY shops, but to really cut down the speed to an acceptable level I would need to use them in a series connection and I have no idea whether that will work or whether it is safe.

You need a different wall control. Try replacing it with a 3 or 4 speed wall control available from anywhere that sells fans.

Ceiling fan remote controls, remote kits, speed controls, dimmer switches and more - at Ceiling Fans 'N More