Based on estimates from the U.S. Department of Labor’s Occupational Information Network, more than half of construction production occupations are exposed to contaminants like pollutants, gases, dust or odors at least once a week.
Thanks to advancing technologies and relatively new standards from the U.S. Occupational Safety and Health Administration (OSHA), industry consciousness over silica exposure has grown in recent years. But that’s just the tip of the iceberg as it relates to air quality for construction, demolition and recycling operators, says Jeff Moredock, the executive vice president for Sy-Klone International, an air cleaning equipment manufacturer based in Jacksonville, Florida.
With Moredock serving as the international project lead for the International Standards Organization (ISO), a new standard of in-cab air quality is on the horizon that could help improve both machine and operator well-being and performance.
But even before that standard comes into play, managers can take steps to ensure their operators have optimal air quality while they work.
Problems with air quality
According to Moredock, in-cab air quality is primarily dependent on four different factors: temperature, humidity, carbon dioxide (CO2) concentration levels and dust particle levels.
Temperature and humidity are easily controlled by most HVAC systems. CO2 and dust, however, are not as simple to address.
Some HVAC systems only recirculate the air inside the cab and some, known as fresh air systems, draw air from outside the cab. Either configuration can present significant air quality problems when operating in high dust concentrations, as one recirculates stale air while the other draws dust into the cab.
“There are issues when you talk about recycling facilities or construction environments, particularly when they're not exposed to the atmosphere—in other words, they're inside of a building. When you're running equipment inside of a building and you don't know how much ventilation you're getting, you can have higher concentrations of all of the different types of particles because you're in there moving things around, crushing, abrading, grinding, whatever you're doing, and you're creating all this dust,” Moredock says. “If the ventilation system, the air intakes, then filtration system cannot remove those particles from the air, they will suck them into the cab. The result of that is you increase the concentration levels of these particulates inside the cab, and the air quality goes from good to not good.”
Dust in the cab can be problematic for both the machine and the operator.
When outside particulates get sucked into the cab, they clog the HVAC system and degrade its function.
But even more problematic is the particulates’ effects on operator health. Dust can contain a variety of contaminants, including silica and asbestos, which can be harmful to operators, especially with long-term exposure.
If the HVAC system is not recirculating air, CO2 also starts to build up in the cab. Moredock says CO2 exposure can also create health problems that may be more immediate, especially with the use of diesel-powered machines. More CO2 equals less oxygen in the cab, which can impair cognitive function and decision-making. It also causes the air to feel stifling, which may result in operators opening a window and exposing themselves to even more contaminants.
Regulations currently exist to quantify safe levels of contamination. OSHA’s recent silica regulations lowered the permissible exposure limit (PEL) to 50 micrograms per meter cubed averaged over an 8-hour day. Similarly, ISO 16000 has established that the CO2 concentration for medium indoor air quality is 800 parts per million (ppm).
Moredock, however, says there is a difference between indoor air quality in a typical building and in-cab air quality in a working environment.
“What we found is the 800 ppm was a good mark for buildings, but … you also have ambient CO2, which is what your CO2 level is just walking around outside, and then you have the CO2 level inside the cab with a guy breathing it,” he says. “What we're really concerned about is the difference between those two and making sure that that difference is not substantial.”
The discrepancy in current standards is part of the reason why Moredock is working to create a new framework for assessing air quality.
Moredock is the international project lead for developing ISO 23875, an air quality control systems and air quality performance testing standard for operator enclosures.
“As it relates to standards that directly address air quality, there are very few. In fact, the one that we're writing is the first one that's been written on an international basis that addresses air quality in an operator cab and provides awareness of this as a problem,” Moredock says.
The standard will establish a testing methodology for evaluating the cab’s performance upon manufacturing, as well as methodology for the cab’s ongoing maintenance. Moredock says the standard will be applicable across the entire supply chain, from original equipment manufacturers (OEMs) to industrial hygienists.
“ISO 23875 is unique because of its emphasis on new and retrofit cab air quality system performance. It applies equally to those who design new equipment and those who retrofit used equipment in the field,” Moredock says. “Improving air quality cannot be the sole responsibility of any one group. As the machine passes through its life cycle, it must be continuously maintained and performance tested to validate its proper function.”
Moredock says he hopes the standard is in place by 2021 at the latest. But until then, there are solutions managers can put in place to maintain good in-cab air quality for their operators.
Keeping the cab well-sealed is an important component. But according to Moredock, keeping fresh air recirculating in the cab is key.
“Fresh air [is important] for two reasons. It dilutes the amount of CO2 that's in the cab by mixing it with ambient air, which has lower levels of CO2, so we're diluting the CO2 in the cab. Then, it performs another function. It puts the cab into a positive pressurization state, which means that we have air coming in through a control source, and then this air must look for a place to get out of the cab,” Moredock explains.
Fresh air, however, can be difficult to come by when in an enclosed working environment.
Moredock says high-efficiency filters can filter air coming into the cab through the HVAC system, controlling the airflow in and out of the cab to minimize CO2 and dust buildup.
Moredock adds that filter pre-cleaners are an important component to help tackle especially dusty environments even before those particles hit the HVAC filter, which prevents clogging. “In the absence of this, you're a victim of whatever dust is outside and how much is there, [and] that relates to how quickly that's going to cause a failure on your air conditioning system,” Moredock says.The National Institute for Occupational Safety and Health (NIOSH) recently published its 2019 Dust Control Handbook for Industrial Minerals Mining and Processing, where it concludes that the most effective cabin filtration and pressurization systems are integrated directly into the HVAC system. Although the handbook pertains to the mining industry, Moredock says the recommendations included are pertinent to all industries.
The handbook’s recommended HVAC components to maintain high air quality include:
- A pre-cleaner that uses high-efficiency filtration to collect and divert a majority of particles before they reach the filter.
- A high-efficiency filter that captures 95 percent or more of toxic respirable particles from the 0.3 to 10 micrograms per meter cubed range. Moredock says while many favor HEPA filters, MERV 16 filters are cheaper, longer lasting and typically enough to do the job.
- A high-efficiency MERV 16 minimum recirculating air unit to filter fresh air as it cycles through the cabin.
- A cabin pressure monitor that can alert operators if pressure dips below a set level.
- A CO2 monitor with real-time readings.
- Unidirectional airflow to ensure a steady supply of fresh air.
With new standards coming up the pipeline, fleet managers can get ahead of the curve by requesting new machines conform with ISO 23875 from the factory and adjusting old machines to create cleaner air in the interim.
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