Hand aspirated pumps usually require 10-15 pumps to draw in an appropriate sample. The goal is to provide a given amount of volume across the sensors. When using sampling tubing, add 1-2 seconds of lag time for each foot of extension hose. Be sure to follow the manufacturer s recommendations for lengths of hose to ensure that the pump operates correctly. Monitors have a recovery time.
Recovery time is the amount of time that it takes the monitor to clear itself of the air sample.
This time is affected by the chemical and physical properties of the sample, the amount of sampling hose, and the amount absorbed by the monitor. One must keep in mind the reaction and lag time as they will affect the recovery time. In order to maintain a high level of safety, each person operating an air monitor must understand about relative response, as the monitor may lead you into a dangerous situation. All monitors are designed to be used for one specific gas, and it is usually the one it was calibrated for. After that statement, one might believe that we would need several hundred monitors to perform emergency response.