The invention relates to an airfuel ratio detection apparatus. Particularly, a simple test device has been designed and fabricated and a method of using such a device, which allows a user to easily distinguish the curable materials that can generate contraction stress in different magnitudes. The switch triggers closing of the valve before the sump is emptied to provide a water seal that prevents escape of gas through the drain. The value it is represented by an equation,it=2. A retaining border defines the playground play surface and contains the layers. A switch having an associated first nonlinear capacitance, selectively couples the first and second capacitors.