Idealy if you have a combustion heater in your home, there should be some means of monitoring the air quality. This is where the Air Quality Monitor comes in, it measures both carbon dioxide and carbon monoxide levels, and displays the results on LED bargraphs. If the concentration of either of these gases rises above a preset level, a loud alarm will sound, which means that you should turn off the heater and open the room up to fresh air. Each bargraph comprises eight LEDs that light invidually to show eight distinct levels. In between values are displaed by lighting two adjacent LEDs. This gives a total of 15 levels that can be displayed. The four lower LEDs are green, followed by two orange and then two red LEDs. An automatic dimming circuit ensures that the LED displays are not too bright at night. In addition, the alarm sounds if any of the top three LEDs light in either display. There are three alarm levels: Main alarm sounds if the top LED lights. This consists of a 64ms-long 4...