These 2 hazard symbols also feature the effects of illusory contours. The yellow hazard symbol create the impression of a circle surrounding the black circle in the middle of the image, while the biohazard symbol creates rings that lie along the other 3 prongs. The circle in the first symbol is interesting as it creates a balance between the yellow and black eements, while the rings in the biohazard symbol is notable because it provides subtle emphasis to the prongs by giving it a white outline of sorts