Patent ID: 9587846
Date: 2017-03-07
CPC Classifications: B01D,B01L,B08B,F24F,G01N

Claim:
1. A ductless fume hood comprising: a hood enclosure comprising an inlet and an exhaust stack, wherein the hood enclosure is open to a room for ingress of room air into the hood enclosure through the inlet for combination with contaminated air generated in the hood enclosure to form an effluent stream; a detection system comprising a photo-ionization detector (PID) configured for detecting a chemical compound in the effluent stream; wherein the hood enclosure is configured to include at least one chemical removal filter; wherein the PID is configured to operate in either a set measure mode or in a set comparator mode, wherein the set measure mode is configured to determine a change in absolute gas concentration relative to a known zero, and wherein the set comparator mode is configured to measure the change in status of the at least one chemical filter related to a normal condition with a new filter; and wherein the effluent stream is drawn into the hood enclosure through the opening; and through the at least one chemical removal filter for egress at the exhaust stack.