Class Code 4251
Envelope Mfg
Class code 4251 covers envelope manufacturing operations in California, from converting paper stock into finished envelopes to machine setup, maintenance, and packaging. The WCIRB pure premium for this class is $4.747 per $100 of payroll — a baseline that reflects the typical loss cost for envelope plants and converters.
What Class Code 4251 Covers
This classification applies to facilities that manufacture envelopes and related paper convertings: feeding and cutting paper/web stock, rotary or flatbed die-cutting, folding, gluing (wet and hot-melt), window insertion, printing/imprinting performed as part of envelope production, creasing, perforating, stacking and packaging. It includes automated folder-gluer lines, converting equipment, conveyors, sheeters, guillotines and associated finishing machinery. Activities such as machine setup, routine maintenance, knife changes, quality inspection and manual packing are part of the class. It does not generally cover purely clerical, sales or off-site distribution work, which are assigned to separate clerical or retail codes.
Who It Applies To
- Envelope converters and dedicated envelope manufacturing plants
- Commercial printers with an on-site envelope converting/finishing department
- Packaging manufacturers that produce paper sleeves, envelopes and mailers
- Machine operators, folder-gluer and die-cut operators
- Maintenance mechanics and production maintenance crews
- Material handlers and packers assigned to envelope lines
Common Job Duties
- Operating and feeding rotary die-cutters, sheeters and folder-gluer machines
- Setting up presses, changing knives/blades and tuning machine settings
- Applying adhesives (hot-melt, cold/wet glues) and installing windows or liners
- Inspecting finished envelopes for print quality, cut accuracy and glue integrity
- Packing, stacking and palletizing envelopes and loading finished goods
- Performing routine maintenance, lubrication and troubleshooting on converting equipment
- Cleaning machines, removing paper scrap and managing waste streams
Common Injury Risks
Understanding the $4.747 Rate
The WCIRB pure premium of $4.747 per $100 payroll represents the estimated loss cost — the portion of premium intended to cover expected claims for this class. To calculate the base loss cost, insurers multiply payroll/100 by $4.747 (for example, $200,000 payroll results in 2,000 x $4.747 = $9,494). Final premiums include this base loss cost plus insurer expense loads, state assessments, policy fees, and adjustments such as your experience modification, classification splits, and any schedule rating or deductible programs.
Cal/OSHA Compliance Requirements
Envelope manufacturing must comply with Cal/OSHA machine guarding and hazardous energy control (lockout/tagout) requirements to prevent entanglement and unexpected startup during service. Employers are required to follow Hazard Communication standards (Title 8 Section 5194) for adhesives, solvents and inks and to implement respiratory protection (Title 8 Section 5144) and ventilation where solvent exposures occur. Good housekeeping to control paper dust, regular noise monitoring and a written injury/illness prevention program are also essential.
How Key HR Helps Employers Under Class Code 4251
A PEO like Key HR centralizes payroll and classification accuracy, provides tailored safety programs and training for machine guarding and chemical handling, and manages workers' comp claims and return-to-work plans to reduce lost-time frequency. Key HR also leverages pooled purchasing power for better insurance placement, tracks experience modification, and delivers on-site or remote safety audits to help lower your overall workers' comp cost for envelope manufacturing operations.
Get a QuoteFrequently Asked Questions
Which employees at my envelope plant are covered under class code 4251?
Employees directly involved in converting paper into envelopes are included: die-cutters, folder-gluer operators, press operators when printing is part of envelope production, maintenance mechanics servicing converting equipment, material handlers and packers. Clerical staff, outside sales and separate shipping functions are typically assigned to different classification codes.
How do adhesives and solvents affect safety and claims for this class?
Adhesives and solvent-based glues increase risks for respiratory and skin exposures, flammability concerns and potential for chemical-related incidents. Proper labeling, ventilation, PPE, substitute products (water-based adhesives) and HazCom training reduce exposures and future claims.
What practical steps can lower our workers' comp premium for envelope manufacturing?
Maintain accurate payroll and classification, enforce machine guarding and lockout/tagout, run preventive maintenance on converting equipment, implement ergonomic lifts and rotation to reduce repetitive strain, provide targeted training on adhesives and hot-melt systems, and use an early return-to-work program. Partnering with a PEO to centralize claims management and safety audits can accelerate these improvements and improve your experience modification over time.
Quick Facts
- Class Code
- 4251
- Classification
- Envelope Mfg
- Pure Premium Rate
- $4.747 / $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.
Get a Quoteor call (800) 922-4133Ready to Simplify Workers' Comp for Class Code 4251?
Key HR provides California employers with pay-as-you-go workers' comp, HR compliance support, and payroll — all through one PEO partnership.