Carbon dioxide fire extinguishers (Op-amp) are one of the most common fire extinguishing agents in cars, server rooms and industrial premises. Their effectiveness directly depends on working pressure, which supports carbon dioxide (CO₂) in a liquid state. But what values are considered normal? Why might pressure drop or exceed acceptable limits? And how can you check a fire extinguisher yourself without contacting a service center?
In this article we will analyze technical pressure standards for carbon dioxide fire extinguishers of different brands (from OU-2 up to OU-80), we will explain how the pressure gauge works and what its color zones mean. You will also find out what risks associated with incorrect pressure - from failure in a fire to cylinder rupture. At the end, we will answer frequently asked questions: is it possible to refill a fire extinguisher yourself, how often a check is needed, and what to do if the pressure gauge needle is in the red zone.
Important: the information is relevant for fire extinguishers that comply with GOST R 51057-2021 and TR TS 032/2013. If your fire extinguisher was manufactured before 2014, the standards may differ - check the product data sheet.
Pressure standards in a carbon dioxide fire extinguisher according to GOST
Working pressure in Op-amp depends on the ambient temperature and the volume of the cylinder. According to GOST R 51057-2021, at +20°C the pressure in the carbon dioxide fire extinguisher should be:
- 🔹 5.7 MPa (57 kgf/cm²) — for fire extinguishers with a volume 2–5 l (for example, OU-2, OU-3, OU-5).
- 🔹 5.5–5.9 MPa - acceptable range for most models.
- 🔹 Up to 15 MPa — maximum pressure when heating up to +50°C (maximum operating temperature).
These values are due to the physical properties CO₂: At room temperature, carbon dioxide is in a liquid state under the pressure of its own vapors. If the pressure drops below 5.0 MPa, this indicates a gas leak or valve malfunction. Excess 6.2 MPa at +20°C may indicate that the cylinder is overcharged - a dangerous condition that can cause rupture.
For clarity, here is a table of standard values depending on temperature:
| Temperature, °C | Pressure, MPa (kgf/cm²) | Condition CO₂ |
|---|---|---|
| -20 | 2,0 (20) | Liquid + gas |
| 0 | 3,5 (35) | Liquid |
| +20 | 5,7 (57) | Liquid (normal) |
| +30 | 6,8 (68) | Fluid (high pressure) |
| +50 | 15,0 (150) | Critical pressure |
Critical point: at +31.1°C pressure CO₂ reaches 7.38 MPa - this is the point of the triple state, after which the gas ceases to be a liquid. Fire extinguishers are designed to operate up to +50°C, but storing them near heat sources (for example, in the trunk of a car in summer) is strictly prohibited.
How to check pressure: pressure gauge and its readings
All carbon dioxide fire extinguishers are equipped pressure gauge — a device for visual pressure monitoring. It is located on the top of the cylinder and is color-coded:
- 🟢 Green zone — pressure is normal (5.5–5.9 MPa at +20°C).
- 🟡 Yellow zone — the pressure is below normal (refilling is required).
- 🔴 Red zone — critical pressure drop (fire extinguisher is inoperative).
To take readings correctly:
- Make sure the fire extinguisher is at room temperature (at least 2 hours in a +20°C room).
- Shake the can 2-3 times to mix
CO₂(liquid may separate). - Look at the position of the pressure gauge needle relative to the color zones.
Errors during verification:
- 🚫 Measuring pressure immediately after frost or heat (readings will be incorrect).
- 🚫 Ignoring shaking (may show a false pressure drop).
- 🚫 Checking the pressure gauge on a tilted fire extinguisher (the arrow may “stick”).
☑️ Correct check of pressure in the OU
Causes of pressure deviations: why it falls or rises
If the pressure gauge needle goes beyond the green zone, this is a malfunction signal. Considerable reasons:
Pressure below normal (yellow/red zone):
- 🔳 Leak
CO₂through a leaking valve or damaged seal. - 🔳 Recharge time has expired (fire extinguishers must be refilled every 5 years, regardless of the pressure gauge readings).
- 🔳 Mechanical damage cylinder (cracks, corrosion).
- 🔳 Low temperature storage (below -20°C), due to which
CO₂turns into a solid state (“dry ice”).
Blood pressure above normal:
- 🔺 Recharging the cylinder (excess
CO₂when refueling). - 🔺 Fire extinguisher heating (for example, in a closed car in the summer).
- 🔺 Pressure gauge malfunction (the arrow may “jam”).
⚠️
Attention: If the fire extinguisher is heated above +50°C (for example, in a fire hazardous area), it cannot be used — risk of cylinder rupture! Let it cool in a ventilated area for at least 12 hours.
What to do if the fire extinguisher is frozen?
If the fire extinguisher has been stored at temperatures below -20°C, CO₂ could turn into a solid state (“dry ice”). In this case:
- Move the cylinder to a warm room (+20°C).
- Do not shake or drop - solid carbon dioxide may damage the valve.
- Wait 24 hours, then check the pressure gauge. If the arrow does not return to the green zone, the fire extinguisher needs to be recharged.
What to do if the pressure is not normal
Actions depend on the pressure gauge readings and the condition of the fire extinguisher:
Arrow in the yellow zone:
- 🔧 Check the date of the last refueling (indicated on the label). If more than 5 years have passed - mandatory recharge.
- 🔧 Inspect the cylinder for corrosion or dents. Fire extinguisher if available dispose of.
- 🔧 If there is no external damage, contact a service center to diagnose the valve.
Arrow in the red zone:
- ❌ The fire extinguisher is not suitable for extinguishing fires! It is dangerous to use - the pressure may not be enough to trigger.
- 🔧 Necessary full recharge with a leak test.
- 🔧 If the cylinder is older than 10 years, it dispose of (service life of metal fire extinguishers is 10 years).
The arrow goes off scale (above the green zone):
- ⚠️ Do not use a fire extinguisher - there is a risk of explosion!
- 🔧 Let it cool (if heating was the cause).
- 🔧 If the pressure has not returned to normal, return the cylinder to re-examination (strength test).
⚠️
Attention: Self-refilling of carbon dioxide fire extinguishers prohibited! This requires special equipment and certified gases. Incorrect filling may result in balloon explosion when heated.
If the fire extinguisher is stored in a car, check the pressure every 3 months - especially before long trips. In summer, avoid direct sunlight (for example, cover the tank with a blanket).
How often to check pressure: GOST regulations
According to TR TS 032/2013 and SP 9.13130.2009, carbon dioxide fire extinguishers are subject to:
- 📅 Annual inspection (visual check of the pressure gauge, housing, seals).
- 📅 Recharge every 5 years (regardless of the pressure gauge readings).
- 📅 Re-examination every 10 years (checking the strength of the cylinder).
For automobile fire extinguishers (OU-2) additional rules apply:
- 🚗 Pressure check every 6 months (during maintenance).
- 🚗 Replacement of the fire extinguisher when the expiration date expires (indicated on the label).
⚠️
Attention: If the fire extinguisher has been used (even partially), it needs to be recharged regardless of the date of the last check. Residual pressure does not guarantee functionality!
Even if the pressure gauge shows normal, a fire extinguisher older than 5 years requires mandatory recharging - the gas could have lost its properties due to micro-leaks or corrosion.
Models of fire extinguishers and their features
There are carbon dioxide fire extinguishers from different manufacturers on the market. Let's look at the most common models and their characteristics:
| Model | Volume, l | Pressure norm at +20°C | Features |
|---|---|---|---|
| OU-2 | 2 | 5.7 MPa | The most compact option for cars. Weight ~5 kg. |
| OU-3 | 3 | 5.7 MPa | Optimal for offices and server rooms. Has a socket with a dielectric handle. |
| OU-5 | 5 | 5.5–5.9 MPa | Industrial option. Equipped with a pressure gauge with an enlarged scale. |
| OU-8 | 8 | 5.5–5.9 MPa | For extinguishing electrical equipment under voltage up to 1000 V. |
Trustworthy manufacturers:
- 🏭 Frost (Russia) - fire extinguishers with reinforced housings for extreme temperatures.
- 🏭 Yarpozhinvest — models with anti-corrosion coating.
- 🏭 Pozhtekhnika — certified for road transport.
When purchasing, pay attention to:
- 🔍 Availability passports and certificate of conformity.
- 🔍 Date of manufacture (service life - 10 years).
- 🔍 Integrity fillings on the security check.
Frequent errors during operation
Even experienced drivers and business employees make mistakes that shorten the life of a fire extinguisher or make it dangerous. Here are the most common:
Mistake 1: Storing in Inappropriate Conditions
- 🌡️ In the summer in the car — the temperature in the cabin can exceed +50°C, which leads to a critical increase in pressure.
- ❄️ In winter in an unheated garage — at -20°C
CO₂freezes, the fire extinguisher becomes inoperative.
Mistake 2: Ignoring checks
- ⏳ Many people forget that a fire extinguisher is needed recharge every 5 years, even if the pressure gauge shows normal.
- 🔍 They don’t check bell integrity — cracks can lead to the scattering of fragments when triggered.
Mistake 3: Incorrect use
- 🔥 Holding a fire extinguisher for the bell when extinguishing - this leads to frostbite on the hands (the temperature of the bell drops to -70°C!).
- 🔥 Direct the stream from top to bottom on the flame (correctly - from the side, tangentially).
To avoid frostbite when using Op-amp, hold the cylinder by the handle, and point the socket at the source of the fire from a distance of 1–1.5 meters. After extinguishing, do not touch the metal parts - they are icy!
FAQ: Answers to frequently asked questions
Is it possible to refill a carbon dioxide fire extinguisher yourself?
No. Refilling requires special equipment (scales for dosing CO₂, compressor, leak tester). Self-refueling is dangerous: the wrong amount of gas can lead to balloon rupture when heated. Contact certified centers.
What to do if the fire extinguisher partially works?
Even if the pressure on the pressure gauge is normal, the fire extinguisher need to recharge. Partial use disrupts the balance of liquid and gaseous phases CO₂, which reduces the effectiveness of extinguishing. Also, check the flare for ice (a sign of a gas leak).
How to check a fire extinguisher for leaks if there is no pressure gauge?
Carbon dioxide fire extinguishers are always equipped with pressure gauges, but if one breaks, use soap solution:
- Apply the solution to the valve and cylinder connections.
- If bubbles appear, there is a leak.
- Fire extinguisher with leak cannot be used!
How much does it cost to recharge a carbon dioxide fire extinguisher?
The cost depends on the volume of the cylinder and the region:
- OU-2: 800–1,200 rubles.
- OU-5: 1,500–2,500 rubles.
- OU-8: 2,000–3,500 rubles.
The price usually includes: refill CO₂, checking the pressure gauge, replacing seals, issuing a new passport.
Is it possible to use a fire extinguisher that has expired?
No. Shelf life of a carbon dioxide fire extinguisher: 10 years (see date of manufacture on the case). After this period, the metal of the cylinder loses its strength, and the risk of rupture increases. This kind of fire extinguisher subject to disposal.