Revised Acme Auto Parts Engineering Controls Paper

Gregory J. Uhlenhake

Columbia Southern University

OSH 6302 Advanced Industrial Hygiene

Dr. Laura Riley

July 8, 2026

This paper examined how Acme Auto Parts (AAP) improved occupational safety through engineering controls. AAP reduced employee exposure to airborne contaminants and machinery hazards by implementing ventilation systems and hydraulic-press safeguards. Eliminating the processes was not feasible, and the customer did not permit AAP to substitute safer chemicals. Therefore, the report focused on appropriate control design, testing, maintenance, and periodic evaluation to ensure that the controls remained effective under workplace conditions.

AAP needed ventilation controls to reduce worker exposure to airborne contaminants in the machining lines, paint booths, and hand-welding stations. The appropriate control strategy depended on how contaminants were generated and moved through the work area. General dilution ventilation was selected for the machining lines because contaminants could have dispersed across a broad area rather than originating from one fixed source. General ventilation supplied cleaner air to the work area and exhausted contaminated air to reduce airborne concentrations. This approach was appropriate when several machines contributed to exposure, contaminant concentrations were relatively low, and source capture at each machine was not practical (American Conference of Governmental Industrial Hygienists [ACGIH], 2024).

The airflow pattern was designed to move cleaner supply air through occupied work areas and toward exhaust points. Exhaust fans were positioned to remove warm, contaminated air where vapor, mist, or heat could have accumulated. Makeup air was supplied from cleaner areas to reduce the movement of contaminants into occupied workspaces. Fan placement was also arranged to prevent contaminated air from moving from one employee’s work station to another (ACGIH, 2024).

The effectiveness of the general dilution ventilation system was evaluated through smoke testing, airflow measurements, and exposure monitoring. Smoke tubes or tracer smoke were used to visualize airflow patterns and confirm that contaminants moved away from employees and toward exhaust points. Air-velocity measurements were used to determine whether air exchange was distributed throughout the work area. When metalworking-fluid mist or other airborne contaminants were present, area and personal air samples were collected before and after installation to determine whether exposures had been reduced. Stagnant-air zones, recirculation, and other airflow problems were also evaluated because they could have reduced system performance (ACGIH, 2024).

AAP used local exhaust ventilation for the paint booths and hand-welding stations because both operations generated contaminants at the source. In the paint booths, overspray and solvent vapors were contained within an enclosure that moved airborne contaminants away from workers and into a filtered exhaust system. Paint booths that directed airflow downward or across the workspace produced a predictable airflow pattern. The airflow moved overspray and solvent vapors away from workers and reduced the spread of paint particles into nearby areas (ACGIH, 2024).

For hand-welding stations, a movable exhaust hood or fume-extraction arm was appropriate because it captured welding fumes near the arc before they reached the welder’s breathing zone. Local exhaust ventilation was most effective when the hood was properly designed, provided sufficient airflow, and was positioned close to the contaminant source. In a study of common welding-fume controls, local-exhaust hood capture reduced welding-fume concentrations in the welder’s breathing zone by up to a factor of nine compared with no controls (Knott et al., 2023).

A spray system placed near high-temperature smoke could improve the capture efficiency of conventional local exhaust ventilation (Guo et al., 2025). This approach could be considered when the ventilation design required additional control of hot smoke; however, the conventional paint-booth enclosure and welding-fume extraction arm remained the primary controls recommended for AAP.

For paint operations, AAP selected an enclosing hood because it surrounded the contaminant source and provided greater control than a less-contained hood design. The enclosure also reduced the airflow required to control contaminants. For hand-welding stations, a movable capture hood or extraction arm was more practical because it allowed the welder to maintain visibility and access to the work while keeping the hood close to the fume source (Knott et al., 2023).

The required flow rate for the painting and welding operations depended on the hood design. The engineering management group selected a plain-opening hood to reduce cost. The team calculated that the hood required a flow rate of \(4{,}200\) cubic feet per minute (cfm) to capture contaminants at the source. The calculation used a capture velocity of \(100\) feet per minute, a hood distance of \(2\) feet from the contaminant source, and a hood opening area of \(2\) square feet (ACGIH, 2024).

Figure 1

Flow Rate Required to Capture Contaminants From Paint and Welding Operations Using a Plain-Opening Hood

\[

Q = V(10X^2 + A)

\]

\[

Q = 100[10(2)^2 + 2]

\]

\[

Q = 4{,}200 \text{ cfm}

\]

Note. \(Q =\) airflow rate in cubic feet per minute; \(V =\) capture velocity; \(X =\) distance from the contaminant source to the hood; and \(A =\) hood-opening area. The hood opening measured \(1\) foot wide by \(2\) feet long. The calculation was adapted from Industrial Ventilation: A Manual of Recommended Practice for Design (ACGIH, 2024).

The calculation showed that placing the hood farther from the welding source required substantially higher airflow to maintain the desired capture velocity. The higher airflow was needed because the hood’s capture zone decreased as the distance from the source increased. Placing the hood closer to the weld improved capture efficiency and reduced the total airflow required (ACGIH, 2024).

Several barriers could have arisen during implementation of local exhaust ventilation in paint and welding operations. In paint booths, these barriers included installation costs, filter and ductwork maintenance, airflow turbulence, and the possibility that employees could disrupt the intended airflow pattern while spraying. In welding areas, challenges included welder movement, workpiece repositioning, and the need to keep the hood close to the arc without obstructing visibility or interfering with production. Employees could also have resisted equipment that was noisy, difficult to use, or slowed their work. These factors mattered because an exhaust system could have been technically appropriate but still performed poorly if it did not fit actual work practices (Knott et al., 2023).

AAP’s engineering management team sought to improve protection for press operators working in the hydraulic-press area. Hydraulic presses could expose workers to moving parts, pinch points, nip points, and crushing hazards. Engineering controls were recommended to reduce the likelihood of injury by incorporating protective measures into the machine or work area. The controls needed to be selected, installed, and maintained so that employees did not have to rely solely on memory or caution to avoid hazards (Li et al., 2025).

Recommended controls for the hydraulic-press area included fixed guards, interlocked guards, two-hand controls, presence-sensing devices, and emergency-stop devices. Fixed guards prevented access to dangerous moving parts. Interlocked guards stopped or prevented machine operation when a guard was opened. Two-hand controls required the operator to use both hands to initiate the press cycle, helping keep hands out of the point-of-operation hazard area. Presence-sensing devices detected entry into a hazardous area and stopped or prevented hazardous motion, while emergency-stop devices provided a means to stop the machine during an emergency. Machine-safety controls were most effective when the selected safeguards addressed the specific hazards and operating conditions of the equipment (Li et al., 2025; Stara et al., 2013).

Before selecting engineering controls, the management team needed to collect information about the hydraulic press and the work performed around it. This information included the type and size of the press, the location of hazardous points, employee tasks, material-handling methods, and maintenance requirements. The team also needed to review past injuries, near-miss reports, production requirements, and the physical layout of the area. This information helped ensure that the selected safeguards matched the actual hazards and how the job was performed (Li et al., 2025).

To evaluate control effectiveness, management compared conditions before and after installation. The evaluation determined whether guards, barriers, interlocks, or emergency-stop devices reduced the likelihood of employee contact with hazardous press components. Injury reports and near-miss records were reviewed to determine whether incidents decreased after the controls were installed. Safety devices also needed to be reliable, effective, and suitable for the specific machine and work process (Stara et al., 2013).

Management reviewed the controls over time rather than relying on a single evaluation. The review included maintenance records, inspection reports, employee feedback, and new incidents or near misses to determine whether the controls remained effective. Regular evaluation identified whether safeguards continued to protect workers as equipment aged, production demands changed, or new hazards emerged. Continuous monitoring, testing, and risk assessment were important for maintaining machinery safety in manufacturing settings (Li et al., 2025).

The most effective ventilation strategy for AAP was general dilution ventilation for the machining lines and local exhaust ventilation for the paint booths and hand-welding stations. General ventilation was appropriate when contaminants were dispersed across a large area and could not be captured effectively at one source. Local exhaust ventilation was more appropriate when contaminants were generated at a distinct source and could be removed before spreading into the work environment. Properly designed, positioned, tested, and maintained ventilation systems provided practical protection from airborne hazards. Periodic reevaluations were necessary because equipment wear, poor maintenance, and process changes could have reduced system effectiveness over time (ACGIH, 2024).

Engineering controls also provided an important means of reducing hazards in the hydraulic-press area. Fixed and interlocked guards, two-hand controls, presence-sensing devices, and emergency-stop devices reduced the likelihood of contact with hazardous machine parts. However, these controls needed to be selected using accurate information about the machine, work area, and employee tasks. They also required regular inspection, maintenance, and review to ensure that they continued to protect employees (Li et al., 2025).

American Conference of Governmental Industrial Hygienists. (2024). Industrial ventilation: A manual of recommended practice for design (31st ed.).

Guo, S., Huang, Y., Wang, Z., Wang, Y., & Zhang, Y. (2025). Comprehensive evaluation of spray arrangement strategies for spray-local exhaust ventilation. Energy and Built Environment, 6(1), 173–186. https://doi.org/10.1016/j.enbenv.2023.10.005

Knott, P., Csorba, G., Bennett, D., & Kift, R. (2023). Welding fume: A comparison study of industry used control methods. Safety, 9(3), Article 42. https://doi.org/10.3390/safety9030042

Li, H., Sun, Y., Adumene, S., Abioye, A., Li, M., & Yazdi, M. (2025). Machinery safety improvement in manufacturing-oriented facilities: A strategic framework. The International Journal of Advanced Manufacturing Technology, 138, 4531–4560. https://doi.org/10.1007/s00170-025-15763-w

Stara, C., Battini, D., Faccio, M., Persona, A., & Sgarbossa, F. (2013). AHP-based methodology for selecting safety devices of industrial machinery. Safety Science, 53, 202–218. https://doi.org/10.1016/j.ssci.2012.09.005