An alarm system is disclosed for detecting and signaling that a human or an animal is in an enclosed space such as a motor vehicle which includes a monitoring device for monitoring temperature in an enclosed space. The monitoring device may specify a minimum and/or maximum temperature, or a range of temperatures in the enclosed space. A detection device detects the presence of a human or animal in the enclosed space when an unacceptable temperature is reached. In the system disclosed, the human or animal is unable to exit the enclosed space, and a signaling device is used to communicate a signal to a receiver outside the enclosed space indicating the presence of the human or the animal in the enclosed space.