1. Industry Status and Safety Prerequisites

Currently, powder coatings account for 10%–15% of the global coatings market, with an annual growth rate exceeding the average level of the coatings industry. Compared to solvent-based coatings, powder coatings are produced and used in powder form, avoiding the hazards of organic solvents, making them safer, more hygienic, and less polluting. However, absolutely safe production operations do not exist. Research and technical personnel and enterprise managers must understand that only by implementing necessary safety measures can powder preparation and coating operations be safe and reliable.

2. Hazards and Protection in Powder Coating Production and Application

Powder coatings are composed of resins, curing agents, leveling agents, pigments, fillers, and other components. The resin acts as a carrier, encapsulating the other components and significantly reducing the direct harm to the human body from any single component. Internationally, it is classified as organic dust, possessing the common characteristics of ordinary dust and posing certain hazards and risks. The core focus of protection is on dust hazard prevention and control.

2.1 Hazardous Characteristics of Powder Coatings

Prolonged direct contact with powder coatings can irritate the eyes, skin, mouth, and respiratory organs. Excessive ingestion through respiration or skin can damage the lungs, blood, and skin, leading to silicosis, skin allergies, or dermatitis. Dust in industrial production can also cause pneumoconiosis, poisoning, dust deposition, allergic diseases, and local tissue damage.

2.2 Production Environment and Dust Concentration Control

Whether in powder manufacturing or coating operations, workshop hygiene and equipment sealing are crucial. Well-sealed, leak-free production and construction equipment must be selected. According to the Ministry of Health's GBZ2-2002 standard, the maximum permissible concentration of general dust in workshop air is ≤10 mg/m³, and dust containing more than 10% free silica is ≤2 mg/m³. There are six main dust generation points in powder production: weighing point, feeding point, extruder feeding point, tablet press receiving point, mill feeding point, and mill discharge point. Dust control methods vary among enterprises of different sizes: small manufacturers often control dust by installing exhaust fans and setting up barriers, primarily to reduce cross-contamination of products; large enterprises design and install dust recovery pipelines, placing suction vents at each dust generation point to achieve instantaneous dust recovery. This not only cleans the environment, ensures product quality and employee health, but also allows for the reprocessing and utilization of recovered dust, achieving economic benefits. For manufacturers that lack the conditions to install a dust pipeline recovery system, the traditional dust prevention "eight-character policy" (reform, water, airtightness, ventilation, protection, management, education, and inspection) can be followed. Based on workshop isolation and fan ventilation, materials should be handled gently during weighing and placement, and dust should be vacuumed when cleaning equipment, sites, and individuals (avoiding the use of compressed air to blow away dust). This reduces the risk of powder spillage, leakage, and spillage, effectively lowering or eliminating dust hazards.

2.3 Personal Protective Equipment (PPE)

In powder production, the direct contact points between personnel and materials are raw material weighing and feeding, and finished product weighing and packaging. Toxic substances and dust mainly enter the body through absorption via the skin or respiratory mucosa (skin injuries accelerate absorption). Operators must wear work clothes, gloves, masks, shawls, and other PPE, and operate according to process requirements to avoid allergic reactions or poisoning.

2.4 Selection Criteria for Protective Equipment

Dust masks: Divided into oil-based dust masks (Class P) and non-oil-based dust masks (Class N), and classified into six categories according to dust filtration performance and dust filtration rate: KN90. KN95. KN100. KP90. KP95. and KP100. KP category is suitable for protection against oily dust (such as paraffin wax, jade oil, etc.), and KN category is suitable for protection against non-oily dust (such as salt, ore, etc.). The higher the number, the higher the dust filtration rate and the stronger the safety factor. Selection should be based on the ambient dust concentration. According to GB2626-2006 standard, dust masks must meet the requirements for inhalation and exhalation resistance, with a constant ventilation coefficient of 85 (±1) liters/minute, a dust filtration rate of ≥90% for dust particles smaller than 5 micrometers in diameter, and a dust filtration rate of ≥70% for dust particles smaller than 2 micrometers in diameter. Two misconceptions need to be corrected: first, gauze masks have a dust filtration rate of only about 10% for dust particles smaller than 5 micrometers, and are not effective at preventing dust; second, wearing a dust mask does not guarantee complete protection against pneumoconiosis, and it must be combined with other protective measures. Dustproof clothing: Because powder coatings easily generate static electricity, dustproof clothing must meet the Class B requirements of GB17956-2000 to avoid safety hazards caused by static electricity.

2.5 Establishment of Safety Protection System

Powder coating manufacturing and coating workshops need to establish and improve prevention systems, the core of which includes controlling the concentration of environmental dust, standardizing operational protective measures (such as wearing dustproof work clothes, dust-filtering respirators, etc.), and reducing long-term skin contact with powder coatings.

3. Safety Management in Powder Coating Process

Powder coating primarily employs electrostatic spraying. Safety issues mainly focus on three aspects: fire and explosion prevention in the powder spraying area, dust pollution control, and cleaning contamination from coating fixtures.

3.1 Fire and Explosion Prevention Requirements for Powder Coating

According to national coating safety standards, the fire hazard zone of the powder spraying area is classified as Zone 22. with a fire hazard classification of Class B; and as a zone 11. it is classified as a hazardous area for explosive dust environments. Relevant standards have clear provisions regarding process design, engineering safety, hygiene indicators, and area settings: Within 10 meters of the powder coating area, no other flammable substances other than the workpieces are allowed to enter; The surface temperature of the workpiece entering the powder coating chamber must be lower than 2/3 of the ignition temperature of the powder-gas mixture, or 28°C lower than the auto-ignition temperature of the powder used; The ground in the powder coating area must be laid with non-combustible or flame-retardant electrostatic conductors or semi-conductors, and electrical equipment must be explosion-proof and dustproof, with all conductors reliably grounded; The distance between the electrodes of the electrostatic sprayer (gun) inside the powder coating chamber and the workpiece, chamber walls, guide plates, hangers, and transport devices must be no less than 250mm, and sufficient distance must be maintained between workpieces to avoid mutual collisions.

3.2 Harm and Protection from High-Voltage Electrostatic Guns

The high-voltage electrostatic generators used in electrostatic powder coating operate within a voltage range of 30–100KV, with a common voltage of 40–60KV. Their current is only 0.7mA (far below the 5mA threshold that can damage human organs), making them inherently safe. However, different individuals have varying sensitivities to high-voltage electrostatics, and some may experience irritation. The following protective measures must be taken:

* Avoid using spray guns with exposed high-voltage electrostatic generators;

* When using high-voltage electrostatic generators and electrostatic separation equipment, pay special attention to preventing leakage from high-voltage cables and discharge at connection points;

* When under load, never touch the discharge electrodes at the nozzle;

* After spraying, promptly connect the spray gun nozzle to a grounded conductor to release residual charge;

* Electrostatic powder guns must be grounded, and operators must wear insulated shoes;

* The voltage of the electrostatic generator should not exceed 90KV, and the spray gun current should not exceed 0.7mA.

4. Enhanced Safety and Explosion-Proof Requirements in Production and Construction

The national safety level for powder coating production and construction has been upgraded from Class D5 to Class B. Testing shows that while powder coatings have a high ignition temperature, the ignition energy of the dust cloud is low. Although the probability of combustion and explosion is lower than that of solvent-based coatings, due to their fine particle size, the use of high-voltage electrostatic coating, and their existence in the air as a mist, when the concentration reaches the explosive limit and encounters an ignition source, a dust explosion is easily triggered, with intensity and destructiveness far exceeding that of solvent-based coatings. Relevant personnel must strictly implement the national standard "Safety Regulations for Coating Operations—Safety of Powder Electrostatic Spraying Process GB 15607" and upgrade any equipment and facilities that do not meet the requirements. When designing production and powder spraying systems, the following requirements must be met:

* Sufficient exhaust volume must be provided to ensure that the dust concentration in the production and powder spraying rooms is always below the explosive limit;

* Pressure relief and explosion-proof measures must be installed in the production system and powder spraying room to automatically release pressure in time during an explosion and reduce damage;

* Enterprises with the necessary conditions may install fire sprinkler systems to prevent explosions.

5. Conclusion

In recent years, safety accidents such as dust explosions and fires caused by short circuits in spray guns during the production and use of powder coatings have occurred frequently. However, through effective process control and reducing the three elements of ignition (combustible material, oxidizer, and ignition source), accidents can be effectively prevented. For example, reducing the concentration of dust in the environment can reduce the total amount of combustible material and lessen the harm of dust to the human body. While powder coatings have relatively environmental and safety advantages, the safety risks in the production and application stages cannot be ignored. Enterprises must strictly implement various safety measures such as dust control, personal protective equipment, fire prevention, and explosion prevention, establish and improve safety management systems, and standardize operating procedures. Operators must enhance their safety awareness, wear protective equipment correctly, and strictly abide by safety regulations. Only by maintaining constant vigilance and ensuring that safety measures are comprehensive and in place can safety accidents be fundamentally prevented, the safety of personnel and property protected, and the healthy and sustainable development of the powder coating industry promoted.