Demand Valve Types Uses Working Principle & Price in Pakistan. Demand Valve is a critical component used in respiratory protection systems and scuba diving equipment. It automatically supplies air only when the user inhures, ensuring efficient air consumption and controlled breathing. as Per (NFPA) Standers.
Demand valves are widely used in:
- Airline Breathing Apparatus (ABA)
- SCBA (Self-Contained Breathing Apparatus)
- Scuba diving regulators
- Emergency escape systems
- Industrial breathing systems
International breathing air safety standards are guided by the International Organization for Standardization and the National Fire Protection Association, while compliance in Pakistan aligns with the Pakistan Standards and Quality Control Authority.
🔎 What is a Demand Valve?
A demand valve is a pressure-sensitive breathing control device that:
- Remains closed until inhalation begins
- Detects negative pressure created by the user
- Opens automatically to deliver breathable air
- Stops airflow when inhalation ends
This mechanism prevents continuous air flow and reduces air wastage.
⚙ How a Demand Valve Works
1️⃣ User inhales through the mask
2️⃣ Negative pressure forms inside the mask
3️⃣ Internal diaphragm moves inward
4️⃣ Valve opens and releases compressed air
5️⃣ Valve closes automatically when inhalation stops
This controlled system ensures efficient breathing and extended cylinder life.
🧰 Types of Demand Valves
1️⃣ Standard Demand Valve
- Supplies air only during inhalation
- Used in airline breathing systems
- Lightweight and economical
2️⃣ Positive Pressure Demand Valve
- Maintains slight positive pressure inside the mask
- Prevents contaminants from entering
- Common in SCBA systems used by firefighters
3️⃣ Diving Demand Valve (Second Stage Regulator)
Used in scuba regulators.
Reduces intermediate pressure air to breathable pressure underwater.
Includes:
- Purge button
- Exhaust valve
- Mouthpiece
- Adjustable breathing resistance (in advanced models)
🌊 Use in Scuba & Emergency Equipment
Demand valves are essential in various systems:
Breathing Air Compressor
Draws in atmospheric air Compresses it through multiple stages Removes oil, moisture, and contaminants Delivers high-pressure breathable air (200–300 bar)
✅ SCBA Systems
Used by firefighters and rescue teams.
Provide 30–60 minutes of air depending on cylinder capacity.
✅ Airline Breathing Apparatus
Connected via hose to an air compressor or cascade system.
Ideal for long-duration industrial tasks.
✅ Scuba Diving Equipment
The second stage regulator functions as a demand valve.
Used with:
- Scuba cylinders (200–300 bar)
- First stage regulator
- Buoyancy Control Device (BCD)
- Submersible Pressure Gauge (SPG)
✅ EEBD Units
Some emergency escape breathing devices use simplified demand systems for compact design.
⚙ Main Components of a Demand Valve
- Flexible diaphragm
- Lever mechanism
- Valve seat
- Spring system
- Exhaust valve
- Purge button (diving models)
- Quick-connect coupling (industrial models)
Each component plays a role in ensuring safe and reliable air delivery.
🏭 Applications in Pakistan
Demand valves are commonly used in:
- Oil & gas refineries
- Shipyards and marine vessels
- Offshore platforms
- Fire departments
- Industrial confined space operations
- Commercial diving operations
Industrial demand is highest in Karachi and other port/industrial cities.
💰 Demand Valve Price in Pakistan
| Type | Estimated Price Range (PKR) |
|---|---|
| Standard Airline Demand Valve | 25,000 – 75,000 |
| Positive Pressure SCBA Demand Valve | 65,000 – 180,000 |
| Scuba Diving Second Stage | 35,000 – 120,000 |
Prices depend on brand, material quality, pressure rating, and certification standards.
🧪 Maintenance & Safety Guidelines
For safe operation:
- Inspect diaphragm regularly
- Check for air leakage
- Clean and disinfect after use
- Test airflow performance
- Replace worn springs and seals
- Service annually by certified technicians
A faulty demand valve may restrict airflow or cause free-flow, both of which are dangerous in hazardous environments.
The Demand Valve is a vital safety component in breathing systems used across industrial, marine, firefighting, and diving sectors in Pakistan. Whether integrated into SCBA units, airline breathing apparatus, or scuba regulators, it ensures controlled, efficient, and safe delivery of breathable air.