Video Exposure Monitoring
Work practices by individuals can make a huge impact on toxic exposures, so evaluating toxic exposures while a person works can make a huge difference. It is not unco9mmon for 90% of a toxic exposure tp occur in 10%%
Initial trials
My initial experience was with workers filling uranium oxides into 200L drums at a uranium mine. We knew that the exposure to radioactive dust was higher than desirable, but we did not know at which stage of the process the exposure was occurring. A Rotheroe and Mitchell laser based dust monitor was attached to a chart recorder while the drum filling operation was performed.
(SIMSLIN picture from Blackford, D. B. and G. W. Harris (1978). “Field Experience with SIMSLIN II–A Continuously Recording Dust Sampling Instrument.” Ann Occup Hyg 21(3): 301-313.)
This study showed that much of the dust exposure occurred during placing the lid on the drum after filling. The process was changed so that the lid was slid onto the drum, avoiding the plume of displaced, dusty air when the lid was placed vertically.
Glove fluorescence unit
This smaller plywood box is for more detailed examination of gloves. It will also be used to quantify colour changes in gloves with use under standardised lighting conditions.
To come: pictures
Digital telemetry system
A prototype system was developed:
- six analogue channels, including heart rate from a Polar heart rate monitor
- video stream from a USB camera
- data logging for 8 hours
- 433 MHz digital telemetry (and receiver for a PC)
- real-time compression of the video signal – a hard disc fills up rapidly with uncompressed video
- breathing zone dust sensor for use inside a welding helmet
- tympanic ear sensors (heat stress)
To come: lots of pictures
During some contract research investigating chemical exposures during the hot refuelling of helicopters, it was realised that the limiting factor with aviation fuel exposure was not the gloves but the work practices. Actions like donning and doffing gloves and touching the face gave direct fuel exposures to the hand a face. A portable florescence system was developed to permit field evaluation of work practices.
Whole body portable fluorescence unit
A light-tight ventilated box was constructed for this work.
Initial trials were performed with a car inspection lamp fitted with a UV tube. These indicated that the unit was acceptable of detecting low levels of skin contamination
Alternate fluorescing compound are being developed
So is a fluorescing stem based on blue light excitation using a conventional electronic flash and optical filters.
Video overlay
Some trials were performed with an old “ForA” video overlay box and a video editing system with some success.
This permitted two video streams to be merged, either as an overlay or as a picture-in-picture.
Video overlay box
This approach was based on the chip found in TV’s and VCR’s that displays the volume as a bar at the bottom of the TV. Electronics Australia (now defunct) has a kit project based on this chip that could interface with a serial port of a PC that would allow text.
A font was created that allowed a box, plus part boxes to be displayed, increasing the resolution from that of a simple block display – plus the value of the toxic exposure.