The Degreaser Risk Rating That Doesn't Match the Sampling

The rating is not defensible as written. The decisive fact is that one of two personal samples exceeded the 8-hour OEL. Once any representative sample exceeds the OEL, the task cannot be treated as a medium-risk operation simply because PPE is worn.

Gaps in the assessment:

• Sample size and representativeness: two samples on one day cannot characterize a task with loading/unloading peaks. The sampling should be task-based and repeated across shifts and operators.
• Averaging period: an 8-hour TWA can hide short, high-concentration peaks. No STEL or ceiling comparison was made, even though degreaser loading is a peak-exposure activity.
• Control verification: the fan belt was replaced but airflow was never measured. A repaired fan is not evidence of adequate capture.
• PPE credited as risk reduction: respirators reduce individual dose only if the program is effective; they do not reduce the ambient hazard and should not lower the inherent risk rating in the hierarchy of controls.
• Health surveillance: headaches and dizziness are nonspecific but temporally consistent; they warrant exposure investigation and medical follow-up, not dismissal.

Before approving a second shift, require repeat personal sampling including STEL/ceiling samples, ventilation airflow and capture-velocity measurements, and a documented statistical basis (for example, an upper confidence limit below the OEL). Until then, the second shift should not be approved.

Apply the hierarchy rather than defaulting to respirators.

Permanent controls to evaluate first

• Substitution: assess an aqueous or less toxic cleaning process, or a closed degreaser design.
• Engineering: enclose the degreaser, maintain correct freeboard and lip exhaust, add refrigerated coils, automate the hoist to reduce operator proximity, and correct duct/fan capacity.

Interim measures while engineering is designed

• Repair and commission the exhaust system and verify airflow before production resumes.
• Reduce batch size, lower bath temperature, and restrict loading to trained operators.
• If airborne concentrations remain above the OEL, use respirators under a full written program: medical evaluation, fit testing, training, and cartridge change schedule.
• Increase symptom surveillance and remove symptomatic workers from exposure pending evaluation.

Decision criteria

• Do not start the second shift until repeat personal samples demonstrate the 8-hour TWA is below the OEL with margin (for example, below 0.5 of the OEL) and peak exposures are below the applicable STEL/ceiling.
• Verify ventilation performance by measured airflow and capture velocity, not by the fan running.
• Re-sample after any process, chemical, or ventilation change, and after the second shift begins to confirm the exposure profile has not shifted.

Reconcile the two matrices before using either score. Confirm whether the corporate and site matrices use the same severity and likelihood definitions and the same number of levels; a score of 8 on a 4x4 matrix is not equivalent to 8 on a 5x5 matrix.

Then calibrate likelihood with the exposure data. An OEL exceedance should drive the likelihood or severity category upward; it is not a 'medium' condition merely because PPE is assigned. Define explicitly how PPE is treated: as a mitigation that may reduce the probability of harm only if the program is verified, never as elimination of the hazard.

Document in the risk register:

• the exposure data, sampling limitations, and assumptions;
• the controls in place and their verification status;
• residual risk after controls, with an owner and review date;
• the decision to withhold or condition the second shift.

Because an OEL exceedance and reported symptoms are involved, escalate the residual risk to management review and communicate the findings and interim precautions to affected workers. Treat the second shift as a management-of-change action requiring re-assessment.