interfacing smoke sensor with uno

I am trying to connect a photoelectric smoke sensor with arduino uno. The smoke sensor IC have pin 7 as I/O pin which gives a 9v when smoke is detected.I have connected this pin to input pin of uno through a simple potential divider.But when i connect sensor to micro it gives false alarm after some time and works fine when independent.
I have kept all the wires short to avoid any capacitive loading and have internally pulled down the pin.
Any leads where i am going wrong

Please let is know which data sheet being used Here. Can you share the datasheet and ciruit layout

What resistances did you use in the divider? They should be probably be large (e.g. 2 x 1 megohm) to avoid loading the smoke alarm output.

smoke sensor is having xc5010dw and i was using 3.9M divider(two 3.9M).
i used a opamp in buffer configuration after divider and it is working now.

Thanks all