VOC Sensor Helps “Clear the Air”
at Hazy Welding Plant

by Terry Noble

A major manufacturing company has come up with a new application for BAPI’s VOC sensor. They’re literally using it to help clear the air at their main fabricating plant.

Building Automation Products, Inc (BAPI), a Wisconsin HVAC sensor manufacturer, originally designed the VOC sensor as an alternative to CO2 sensors for demand-controlled ventilation, but a growing number of facilities with specific substance concerns are finding that it is a good solution for them as well. In this case, the offending substances were the byproducts of welding.

Greenheck Fan Corporation is the industry-leader in the manufacture of HVAC air movement and control equipment. Greenheck contacted BAPI last year while looking for a cost-effective way to improve air quality at their main welding facility in Schofield, Wisconsin. Specifically, they were looking for a way to control exhaust fans and bring in conditioned outside air only when necessary. The goal was to maintain good air quality and as a bonus, save energy. BAPI’s suggestion to use the VOC sensor turned out to be a great success.

“There was a haze in the air at the plant,” Greenheck Manufacturing Engineer Brent Mattson explained. “We had complaints from staff about the haze even though the air quality was within OSHA specified levels.”

Greenheck took the complaints seriously; especially considering recent findings that overexposure to two components in welding fumes, manganese and hexavalent chromium, can cause brain damage or lung cancer. While a VOC sensor does not specifically sense weld smoke or particulates, it can provide a way to maintain good air quality even in a welding atmosphere.

The 138,000 square foot facility has 30 welding bays, each with a source capture hood venting air to the outside. There are also five rooftop exhaust fans and three makeup air units supplying conditioned air. Running all the vents at once all day was expensive and probably unnecessary, but they had no way to accurately measure if and when additional ventilation was necessary – until they tried the VOC sensor.

Greenheck was able to use their team’s extensive HVAC knowledge and experience as well as their industrial controller to design a custom system. Now the hoods, fans and makeup air units are all communicating with each other and with six BAPI VOC sensors located throughout the building.

“We’re saving money,” said Mattson. “And we compared the results of the air sampling with the new system to the OSHA standard and we’re well below the standard.”

The utility costs at the facility have dropped from 3.5% of the total cost to under 3% since installing the system, and Greenheck expects to recoup the cost of the project in about 1.8 years. They also received a $12,000 grant from Focus on Energy to help offset the $40,000 cost of the project.

According to Mattson, the savings is nice, but keeping the staff healthy and happy is the most important part. “There is no longer any haze and no longer any complaints about the air quality,” he said.

Applications Growing for Versatile Sensor

BAPI’s Volatile Organic Compound (VOC) sensor was originally designed as a direct replacement for a CO2 sensor in demand-controlled ventilation. Just like a CO2 sensor, it can tell when a space is occupied because it detects human-generated VOCs, but it also detects contaminants from other sources such as building materials, cleaners, perfumes, furniture, equipment and carpet off-gassing. These are the types of contaminants that can adversely affect human health and productivity and yet are invisible to a CO2 sensor.

A growing number of facilities with specific substance concerns are finding that their best solution includes a BAPI VOC sensor. This sensor has proven effective at sensing contaminants as diverse as formaldehyde at a cadaver lab, rocket fuel at a defense contractor and human sweat in gyms and exercise centers. It has even been used to tell when the outside air has high levels of automobile exhaust or forest fire smoke.

For more information on BAPI’s VOC sensors, go to