We used five different types of real-time airborne particle monitors in our outdoor study of tobacco smoke. With these instruments, we were able to measure air pollution every few seconds or minutes, and, therefore, to pinpoint the high peak levels of air pollution that could occur. Another benefit of these instruments was the ability to correlate pollution levels directly with the presence of active cigarettes. An important feature of most of the instruments was their small size and portability. They are kind of like having a "laboratory in a lunch box". These small particle monitors are a major technical leap from the old pump-with-filter way of making particle measurements, which requires collecting material on a filter and weighing it later in a formal lab facility.