The top shelf (highest level) is suitable for placing the following types of items, mainly based on a comprehensive consideration of safety, accessibility, and item characteristics:

✅ Recommended Item Types and Reasons

1. Lightweight and bulky items
- *For example*: Holiday decorations (lanterns, ribbons), empty cardboard boxes, inflatable toys, quilts/down duvets, etc.
✔️ Advantages: Utilizing high-level space saves floor area and prevents damage to lower items; light weight prevents deformation due to gravity or low risk of falling.
⚠️ *Note*: Ensure stable stacking; ropes can be used for fixation to prevent accidental falls.

2. Seasonal supplies used infrequently
- *For example*: Winter thick clothes, skiing equipment (summer storage), camping tents (off-season), spare tires, etc.
✔️ Logic: "High places are cold" - placing items used only a few times a year in the hardest-to-reach place reduces daily interference.
💡 *Tip*: Attach clear labels indicating the contents and storage date to facilitate cleaning up expired items at the end of the year.

3. Durable goods with low dust and moisture requirements
- *Such as*: Tool accessories in plastic storage boxes, unopened paint cans (when well-sealed), large packaging groups of hardware parts.
✔️ Scientific basis: Warehouse studies show that air circulation is faster at the top, and the humidity is relatively low, which helps maintain dryness (refer to ISO warehouse standards). However, it should be kept away from windows to prevent sunlight from aging the material.

4. Standard boxes/pallets of uniform specifications (warehouse scenario)
- *Applicable objects*: Full boxes of fast-moving consumer goods in e-commerce warehouses, library archive boxes, parts classification inventory units (SKU).
⚙️ Automation matching: Used with forklifts or lifts to achieve FIFO (first-in, first-out) management; centralized placement of similar goods improves inventory efficiency.
❗Restrictions: The weight of a single box should not exceed the employee's safe handling limit (usually ≤15kg/person).

❌ Absolutely prohibited hazardous goods

| Danger Level | Typical Examples | Risk Consequences
||-||
| ⭐High Risk⭐ | Glass bottle liquid chemicals | Falling and breakage + corrosive leakage
| | Heavy mechanical parts | Center of gravity too high, leading to shelf collapse accidents
| | Flammable and explosive gas cylinders | High temperature environment causes explosion
| ⚠Medium Risk⚠ | Frequently used office supplies | Frequent climbing increases the probability of work-related injuries
| | Precision instruments and electronic equipment | Vibration causes internal components to loosen and damage

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📌 Summary of Golden Principles

1. Law of mechanical balance → Heavy objects at the bottom, light objects at the top; bottom load does not exceed 80% of the rated load of the shelf (leave a safety margin).
2. Human factors adaptation → Design storage locations based on the average height of employees: Top height = maximum reachable height + comfortable operating area after using a footstool.
3. Dynamic adjustment mechanism → Review item turnover rate data every quarter; if an item is moved >3 times/month, it should be downgraded.

🌰 Actual Case Comparison

| Scenario | Correct Practice | Incorrect Demonstration
|-||-|
| Supermarket beverage area | A layer (top): Cases of mineral water | ×Top layer places edible oil bottles (easily broken)
| Home garage converted storage room | B layer (middle): Commonly used gardening tools | √Top layer places Christmas tree lights (used once a year)
| Laboratory chemical cabinet | C layer (bottom): Concentrated sulfuric acid reserve tank | ×Top layer places ethanol spray bottle (volatile and explosive)

📐 Advanced Techniques (Applicable to Professional Warehousing)

For intelligent warehouses using WMS systems, the top-level utilization rate can be optimized using the following formula:
`Top priority index = (Item volume × Storage cycle length) / (Single outbound frequency × Single item weight)`
The higher this value, the more suitable it is for the top level, maximizing space efficiency with a layout of 'heavy and bulky items at the bottom, and slender, stackable items at the top'.