24 The Synergist n March 2013

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FEATURE | VEM Goes Mobile

VEM Goes Mobile

“Helmet-cam” Allows Video Exposure Monitoring 

for Mobile Workers

by gerald joy
Since the 1980s, video exposure monitoring (VEM)—a 

method that combines video 

monitoring with datalogging environmental instruments—has 

been used to evaluate exposures 

for workers during job activities 

that are performed in relatively 

fixed locations. Over the years, 

advances in video recorders, video 

file formats, exposure monitors, 

and software have increased VEM’s 

viability as a monitoring method. 

However, one aspect of VEM has 

not changed: the restriction of its 

application to fixed work locations. 

The challenge of monitoring mobile workers—workers who do not 

have a fixed work location such as 

a plant or mill, or who do not work 

inside a cab with an effective aircleaning system—persists.

It can be difficult to identify source(s) 

of exposure for mobile workers, given 

the variety, number, and brevity of 

tasks that may be assigned; the multiple 

work locations involved; and transient 

effects from weather conditions and 

other nearby work activities. Traditional 

time-study methods provide the necessary information, but this approach is 

labor intensive. Worker self-evaluations 

may be used as an alternative, but this 

method requires supplemental training 

of the work force and careful analysis of 

the reports to control potential biases. 

The self-evaluation method also adds 

duties to workers who may already be 

overtaxed. 

But now modern technology allows 

for VEM to “go mobile.” Researchers 

from the NIOSH Office of Mine Safety 

and Health Research (OMSHR) are working on a potential solution to provide 

insight into the sources of exposures for 

mobile workers: mobile video exposure 

monitoring (M-VEM). M-VEM has already served as a useful tool in exposure 

monitoring for mobile workers. For 

example, elevated respirable crystalline 

silica (quartz) exposures have been identified among a group of surface mine 

workers, including mobile employees 

such as mechanics, laborers, and oiler/

greasers, through traditional sampling 

methods. Using M-VEM, OEHS staff were 

able to pinpoint the sources of exposure—not possible with time-weighted 

average samples—and work to eliminate 

the hazard.

Figure 1. A worker equipped with a video 

recording camera and dust sampler.

Figure 2. Detail of the camera mounted 

on a worker’s hard hat.

Figure 3. Detail of dust sampler inlet location (10-mm Dorr-Oliver nylon cyclone).

“Helmet-cam”

Researchers have casually labeled 

M-VEM “helmet-cam” because of the 

monitoring camera attached to the worker’s hard hat. This method of exposure 

monitoring utilizes a small commercial 

off-the-shelf video camera/recorder and 

an appropriate datalogging exposure 

monitor to be worn by the worker being 

studied. Other than the initial deployment of the equipment and orientation 

of involved workers, little oversight is 

required to make use of M-VEM. Mobile 

workers are able to perform their normal 

activities with minimal interference while 

gathering video and exposure data simultaneously. One configuration of the personal video recorder and respirable dust 

exposure monitor being worn by a worker 

is displayed in Figures 1, 2, and 3.

A note about gathering video and 

exposure data simultaneously: one 

of the pioneering reports on the VEM 

method discussed an issue that the authors termed “system response time” 

or “transportation lag.” This lag is the 

combination of the delays associated 

with movement of the contaminant from 

its source to the worker’s breathing zone 

and the response time of the monitoring 

instrument. As a result, the concentration values reported by the monitoring 

instrument trail the activity displayed in 

the video image. The magnitude of this 

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March 2013 n The Synergist 25

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26 The Synergist n March 2013

FEATURE | VEM Goes Mobile

delay must be recognized, particularly 

if the activity under study exhibits periodic emissions peaks, or in the case of 

M-VEM, if the worker moves through 

multiple exposure environments.

Integrating Software

As with fixed VEM systems, the video 

and exposure data files must be combined to create a usable product. In the 

OMSHR M-VEM system, integration 

of the collected information is accomplished through a Windows-based software application called Enhanced Video 

Analysis of Dust Exposure, or EVADE. 

EVADE combines the exposure data file 

and the video file, performs some basic 

analysis, and facilitates further analysis of the information through graphic 

representation of exposure data and the 

synchronized video file. 

Figure 4 is a screenshot that depicts 

a full view of the EVADE dust application. The video window occupies the 

largest portion of the screen and a line 

graph of exposure concentration vs. 

time is at the bottom of the screen. The 

exposure concentration is presented on 

the Y-axis in user-selectable units of 

μg/m3 or mg/m3. The formatted horizontal lines on the graph are optional 

user-defined criteria (action level, exposure limit, etc.). The concentration 

shown next to the word “Reading” is 

the value corresponding with the video 

image. 

The upper left portion of the screen 

in Figure 4 contains information and 

command functions arranged in tabs. 

The “Active Bookmarks” tab is open 

and the vertical red lines on the graph 

below mark the bookmark locations. 

EVADE automatically bookmarks the 

five highest concentration peaks. The 

user can add up to 45 additional bookmarks, which allow for rapid navigation 

through the data. Selecting a bookmark 

moves the both video and concentration 

files to that point in time, facilitating 

quick analysis. 

The respirable dust version of the 

EVADE software application and supporting user’s manual are available for 

free download on the NIOSH website at 

www.cdc.gov/niosh.

Figure 4. Screenshot from the EVADE software application.

Benefits of M-VEM

During development testing, M-VEM 

was able to provide useful information 

on the sources of exposures to mobile 

workers, and even helped to identify 

sources of unexpected exposures. In one 

case, M-VEM identified an exposure to 

respirable dust in a facility’s breakroom, 

even though the room was frequently 

cleaned and no apparent dust source 

was present. When the facility investigated the situation, it was determined 

that cloth-upholstered chairs in the 

breakroom had become reservoirs of 

respirable dust following years of use 

and that the dust was aerosolized when 

workers occupied the chairs. The facility 

replaced the chairs with non-upholstered 

furniture, and added cleaning the chairs 

to the maintenance of the room. Subsequent respirable dust sampling reported 

elimination of the issue. In a setting that 

would not typically be monitored and 

that would probably not be included in a 

time study or self-reporting protocol, MVEM’s ability to identify the presence of 

an exposure source demonstrates one of 

its most important advantages.

Beyond exposure source characterization, M-VEM offers the opportunity to 

use exposure data collected via EVADE 

as a training tool, both for new workers 

and for reinforcing desired behavior in 

current workers. Together, the video and 

exposure concentration data effectively 

demonstrate the effect of a worker’s actions and location on exposures. Using 

M-VEM and EVADE, OEHS professionals 

can clearly illustrate the consequences of 

work techniques, such as dry sweeping vs. 

vacuuming, and even workers’ positioning with regard to a contaminant source.

Limitations

M-VEM has its limitations, some of 

which may be subject to technical improvement going forward. One key issue 

is that the operation of the camera and 

the exposure monitor must be synchronized to ensure that the video image 

closely matches the collected exposure 

data. Currently, the only way to accomplish this synchronization is to manually 

start the two devices as close to the same 

time as possible. Improved options to 

address this issue are being investigated, 

but the variation in how the available 

devices operate is a barrier.

The video camera presents several issues as well, including large file sizes that

exceed 0.5 gigabytes/hour, battery life

that is realistically less than two hours, 

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and multiple video file formats. EVADE 

currently supports .avi and .mp4 file 

formats, although the user may need to 

install additional video codecs (software 

that permits video files to be played). 

File format is selected by the camera 

manufacturer and is usually not variable. 

File format converters are available that 

may be able to generate a usable file, but 

compatibility should be verified before 

purchasing any equipment.

Limited battery life is a consequence 

of the small size and low weight that 

is a major consideration for the typical 

user of these cameras. They are normally 

intended to be worn by people engaged 

in sporting activities such as skiing, 

surfing or biking. Exposure assessment 

is an unforeseen use of these cameras, 

but their small size and low weight are 

advantages for this application as well. 

Researchers have found one camera 

model that will reliably record for four 

hours—a reasonable time frame for conducting exposure assessments, but it is a 

larger two-piece device that uses disposable batteries. Future design advances in 

these cameras may address this barrier 

for camera use in exposure assessment.

Future Work

Because the initial focus was the identification of respirable dust exposure 

sources, the current helmet-cam method 

uses a data-logging nephelometer as the 

exposure monitor. Work is underway 

within OMSHR to expand the EVADE 

application to work with other instruments, including noise dosimeters and 

elemental carbon monitors (surrogate 

for diesel engine emissions). Any instrument that can export a file that can 

be imported into spreadsheet format 

can potentially be used in M-VEM. 

The EVADE software needs to “know” 

where the time and exposure data values (concentration, noise level, etc.) are 

located—row and column in spreadsheet 

terminology. This location is affected 

by headers and other identifying data 

added by the exposure instrument software. In most cases, custom functions 

can be coded to parse the spreadsheet 

file for use in EVADE. Unit of measure 

is another variable applicable to the 

contaminant being measured, but this is 

also straightforward to modify.

Researchers are looking into the possibility of incorporating non-invasive 

biological monitoring, such as heart 

rate and skin temperature. This has been 

demonstrated in VEM systems, and 

should be feasible for M-VEM as well.

Wireless communication of the video 

and exposure data to a base location 

may be another consideration for the 

future. The mining industry is adopting 

two-way communication systems that 

allow for contact between individual 

underground miners and control centers, 

both underground and on the surface, 

for routine and emergency purposes. It 

may be possible to adapt these technologies to the M-VEM model.

M-VEM ultimately allows OEHS staff 

to identify and quantify exposures of 

mobile workers in a time-resolved manner without significantly interfering with 

the workers’ activities, or requiring staff 

to shadow mobile workers. Although it is 

not fully developed, M-VEM shows 

promise as a useful new tool for exposure assessment. 

Gerald Joy, CIH, CSP, is an industrial hygienist at the 

NIOSH Office of Mine Safety and Health Research in 

Pittsburgh, Pa. He can be reached at (412) 386-4074 

or gej3@cdc.gov.

About OMSHR: The mission of the NIOSH Office 

of Mine Safety and Health Research (OMSHR) is 

to eliminate mining fatalities, injuries, and illnesses 

through research and prevention. A primary objective established under this mission is the reduction of 

pneumoconiosis and silicosis among mine workers.

Disclaimer: The findings and conclusions in this 

article are those of the author and do not necessarily represent the views of the National Institute for 

Occupational Safety and Health.

Little oversight is required to make use of M-VEM. 

Mobile workers are able to perform their normal 

activities with minimal interference.

Readings

“Analyzing 

Workplace Exposures Using 

Direct-reading 

Instruments and Video Exposure 

Monitoring Techniques,” DHHS 

(NIOSH) Publication Number 92-

104 (1992).

“A Review of Video Exposure Monitoring as an Occupational Hygiene 

Tool,” Annals of Occupational Hygiene (2005).

“Correlation of the Exposure to a 

Pollutant with a Task-related Action or Workplace: The CAPTIV2 

System,” Annals of Occupational 

Hygiene (1999).

“Detailed Work Analysis for Control 

of Exposure to Airborne Contaminants in the Workplace,” Applied 

Occupational and Environmental 

Hygiene (1995).

“From ‘Wow!’ to ‘What’s Next?’ The 

Future of Video Exposure Monitoring,” The Synergist (January 2010).

“Video Exposure Assessments of 

Solvent Exposures in University 

Pharmaceutical Laboratories—A 

Pilot Study,” Chemical Health and 

Safety (2003).

“Video Exposure Monitoring—A 

Means of Studying Sources of 

Occupational Air Contaminant Exposure, Part I—Video Exposure 

Monitoring Techniques,” Applied 

Occupational and Environmental 

Hygiene (1993).

“Video Exposure Monitoring—A 

Means of Studying Sources of Occupational Air Contaminant Exposure, Part II—Data Interpretation,” 

Applied Occupational and Environmental Hygiene (1993).

“Video Exposure Monitoring: The 

Wow Factor—Learn Why Your 

Workers Are Overexposed,” The 

Synergist (October 2009).

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