Do you know what "Over" means on this QRae 3 meter's display?
Today, while teaching a confined space entry course in Elizabethtown, KY, students were preparing to go into a sanitary sewer manhole for a training scenario. At the beginning of the pre-entry evaluation, air monitoring results appeared all within acceptable limits. However, while still testing the atmosphere inside the manhole, a rush of water came into the space, causing the students to see the results shown in the picture.
Needless to say, we did not enter that manhole, but it started a great discussion and emphasized the importance of continuous air monitoring due to how quickly things can change!
Always take the same precautions during training as you would during a real-world scenario!
Comments (6)
Over the range for that sensor, which I believe is 100ppm for H2S (that is also the IDLH for H2S).
There's a couple of reasons this could have happened with the rush of water you likely saw a spike of gas under pressure which took the sensor over range or possibly a response to the sudden pressure change on the sensor as some electro-chemical sensors can read a positive reading with sudden increase in positive pressure. Would suggest regardless of if it was gas or pressure you recalibrate the unit after the exposure.
I know you guys do consulting, but a good solution if you have yard or space out back of your office...we constructed a sewer manhole for training purposes not connected to city service. We used left over/lightly damaged pre-cast material from a county job and buried it 4 feet deep.