The PeCOD COD Analyzer has a warning label on the analyzer head “DO NOT OPEN ANALYZER LID WHILE IN OPERATION” and “CAUTION: CLASS 3B INVISIBLE LASER RADIATION. AVOID EXPOSURE TO BEAM.” See Image 1.
Image 1: Warning label on analyzer lid
There are two normal LED lights (one red, one green), and one (invisible) Class 3B UV LED laser.  See Image 2.
The red LED light is an error indicator and is a non-harmful light.  The green LED light is the power indicator and is also a non-harmful light.
The Class 3B UV LED laser is a catalyst for TiO2 oxidation of organics.  Class 3B UV LED lasers are harmful to your health, however, there are safety measures put into place to avoid exposure to this invisible UV LED laser on the PeCOD COD Analyzer.  The PeCOD has an automatic laser shut off built in so the laser will turn off when the analyzer lid is opened.  This lid should not be tampered with or modified as the Class 3B laser is hazardous to your health.
Image 2: Analyzer head with 2 (two) normal LED lights, and 1 (one) 3B UV LED Laser