Class Code 4239
Paper Or Cardboard Stock Mfg; Fiber Products Mfg
Class Code 4239 covers employers engaged in manufacturing paper, cardboard stock and fiber products — from corrugating and converting to carton and fiberboard production. The approved pure premium rate for California effective September 1, 2026, is $3.735 per $100 of payroll, which reflects the industry’s loss experience and hazard profile.
What Class Code 4239 Covers
This classification applies to facilities that produce paper stock, corrugated and folding carton stock, cardboard boxes, fiberboard, paperboard converting and related fiber products. It includes primary paper machine operations (wet end and dry end), corrugating and laminating lines, slitting and rewinding, die-cutting and folder-gluer operations, adhesive and coating application, baling of scrap, and routine maintenance of those machines. Converting plants that take large parent rolls and slit, crease, fold, glue, or box them for finished goods fall squarely under 4239. Warehousing tasks directly tied to the manufacturing line (roll handling, palletizing finished cartons) are typically included, while purely clerical or retail functions are usually classified separately.
Who It Applies To
- Paper mills and pulp-converting operations
- Corrugated box and folding carton manufacturers
- Cardboard sheet and paperboard converters
- Fiberboard and specialty fiber product manufacturers
- Plant operators, production line workers, and maintenance mechanics
Common Job Duties
- Operating paper machines, corrugators, laminators, and folder-gluer lines
- Feeding and positioning large parent rolls, roll changing and splicing
- Slitting, rewinding, die-cutting, creasing and trimming finished stock
- Applying adhesives, coatings, starch and varnishes on machines
- Baling and compacting scrap cardboard and fiber for recycling
- Routine mechanical maintenance, lubrication and lockout/tagout
- Material handling: forklift and manual palletizing of heavy rolls and stacks
Common Injury Risks
Understanding the $3.735 Rate
The pure premium rate of $3.735 per $100 of payroll is the WCIRB-approved loss cost reflecting expected claim payments for this class; it does not include insurer expenses, profit, or credits. Insurers multiply payroll by the rate to get a base loss cost and then apply experience modification factors, policy-level expense loads, credits (safety programs, dividend plans), and any deductibles to determine the final premium. Factors that materially affect what an employer actually pays include the company’s loss history (E-mod), payroll mix, classification splits, filed deductible or retrospective plans, and implemented loss-control measures.
Cal/OSHA Compliance Requirements
California employers in paper and fiber manufacturing must follow Cal/OSHA Title 8 requirements that are especially relevant here: machine guarding and lockout/tagout for rotating equipment, respiratory protection and exposure monitoring for dust and solvent vapors, hazard communication for adhesives/solvents, hearing conservation for high-noise operations, and combustible dust awareness and housekeeping to prevent dust accumulations. Employers are required to maintain written programs (respiratory protection, hearing conservation, hazard communication, LOTO), provide training in workers’ primary language, and perform periodic exposure assessments and equipment inspections.
How Key HR Helps Employers Under Class Code 4239
A PEO like Key HR helps manufacturers in Class Code 4239 by conducting classification audits to ensure payroll is assigned correctly, implementing site-specific safety programs (machine guarding, combustible dust controls, respiratory protection), and managing claims and return-to-work plans to lower experience modification. Key HR also provides employee training, incident investigation support, coordinated medical management and OSHA-ready documentation — all of which can reduce claim frequency, severity and overall workers’ comp costs.
Get a QuoteFrequently Asked Questions
Are warehouse or shipping employees included in class code 4239?
If warehouse or shipping tasks are performed as part of the manufacturing operation (handling finished rolls, palletizing cartons from the production line), they are commonly included in 4239. Separate clerical, retail or unrelated distribution-only payroll should be classified to the appropriate non-manufacturing codes to avoid misclassification.
What are the top actions to reduce workers’ comp cost for this class?
Prioritize machine guarding and LOTO compliance, enforce dust control and housekeeping, establish a hearing conservation and respiratory program, train workers on safe roll handling and ergonomics, and implement a formal early return-to-work program to limit claim duration and severity.
How does combustible dust affect compliance and insurance exposure?
Paper and fiber dust creates both a health and an explosion hazard. Employers must evaluate dust accumulation, apply controls (ventilation, dust collectors, housekeeping), and document hazard assessments. Insurers and underwriters will view documented dust-control programs and housekeeping records favorably when pricing coverage.
Quick Facts
- Class Code
- 4239
- Classification
- Paper Or Cardboard Stock Mfg; Fiber Products Mfg
- Pure Premium Rate
- $3.735 / $100 payroll
- Effective Date
- September 1, 2026
- Source
- WCIRB Approved Filing
Manage Workers' Comp Through a PEO
Key HR provides pay-as-you-go workers' comp for California employers — no large deposits, no audits, better rates.
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