1. Composition and Chemical Properties
1.1 Scientific Formulation of Dry Powder
Dry powder fire extinguishers are composed of inorganic salt fire-extinguishing base materials (over 90%), combined with water-repellent agents (e.g., silicone oil), flow enhancers (e.g., mica powder), and anti-caking agents (e.g., magnesium stearate). Key characteristics include:
- Particle size: 20-75μm (verified by laser particle size analysis)
- Propellant: High-pressure carbon dioxide
- pH value: 8.5-9.2 (slightly alkaline)
1.2 Comparison of Fire Extinguisher Compositions
| Type | Main Components | Conductivity | Corrosiveness | Temperature Range |
|---|---|---|---|---|
| Dry Powder | Ammonium phosphate/Sodium bicarbonate | Non-conductive | Slight | -20℃ to 50℃ |
| Foam | Fluorocarbon surfactants | Conductive | Moderate | 5℃ to 40℃ |
| CO₂ | Liquid CO₂ | Non-conductive | None | -30℃ to 49℃ |
| Water-based | Deionized water + Additives | Conductive | None | 4℃ to 45℃ |
2. Fire Extinguishing Mechanisms
2.1 Triple-Action Mechanism of Dry Powder
- Chemical Inhibition: PO₃⁻⁴ radicals interrupt chain reactions (verified by FTIR spectroscopy)
- Physical Cooling: Absorbs 650J/g during decomposition (DSC test data)
- Oxygen Depletion: Releases CO₂ to reduce O₂ concentration below 15%
2.2 Comparison of Extinguishing Mechanisms
- Foam: Forms a >7mm layer to block oxygen (NFPA 11 requirement)
- CO₂: Reduces O₂ concentration below 12.5% (OSHA standard)
- Water-based: Absorbs 2257J/g during vaporization (based on Joule’s Law)
3.Practical Application Scenarios
Best Use Cases for Dry Powder
- Gas stations (Class B fires): Extinguishes 200m² oil fires in 8 seconds (UL-certified data)
- Electrical rooms (Class E fires): Safe for live equipment up to 35KV
- Laboratories (Class D fires): Special sodium-based powders for magnesium/titanium fires
4.Certifications and Regulations
- EU standards: EN 615-2009
- UL certification: Must pass UL 299 testing
发表回复