Model 660 Air Velocity Monitors are a practical, affordable way to continuously monitor for safe airflows through laboratory fume hoods. They are typically installed in the fume hood side fascia and connected to the interior sidewall via 1-1/8" flexible tubing. As the exhaust fan draws air through the device, a sensitive constant temperature thermistor measures flow and lights a green (normal), yellow (high) or red (low) LED. An audible alarm also warns of low flow and requires manual resetting. Mounting holes fit standard single gang electrical box.