How to Choose and Why Use Leak Detectors?

How to Choose and Why Use Leak Detectors?

Refrigerant leak detection

The chart below shows the most common groups of refrigerants we use. With the wide variety of refrigerants available now, we have to ensure that the type of leak detectors we are using is both suitable and SAFE to use with the refrigerant in the system. Most electronic leak detectors are suitable for CFC, HCFC, and HFC’s. Caution should be taken to use suitable electronic leak detectors with HC’s which are flammable. We must not forget soapy water as a very effective leak detector. Many people discount it, but for finding leaks, it is possibly the most effective method, and lots of people have certainly used it to successfully find some very small leaks.


Chlorofluorocarbon, e.g., R12, R502, R11


Hydrogenated, e.g., R22, R409A, R408A, R411B


Hydrofluorocarbon, e.g., R134a, R404A, R407C, R410A


Hydrocarbon, e.g., R600a, R290, CARE

Here is a table which we hope will help you visualize and memorize the suitability of leak detectors for different types of refrigerant. Extra care should be taken when selecting an electronic detector for Hydrocarbon (HC) refrigerants. If in doubt - use soap and water instead.

types of leak detectors and their usage

1. Electronic leak detectors:

For the most part, there are just four types of electronic leak detectors.

  • Corona discharge
  • Heated diode
  • Infrared
  • Ultrasonic

Corona discharge detectors pull air through an electrical field (corona discharge) around a wire. The presence of refrigerant or other gases in the air changes the current in the wire and triggers an alarm. The problem with this is that it’s not compound-specific, so any substance the leak detector senses could give false alarms, including cleaning chemicals. Not HC suitable!

corona discharge electronic leak detector

Heated diode detectors use a heated ceramic diode. This diode generates an electrical current when it comes into contact with halogenated gas which the electronics convert into an alarm. The heated diode sensor is sensitive to contamination, especially from moisture or oil, and will need replacement after approximately 100 hours of operation. This type of detector is much less likely to give false alarms and works especially well with R134a. The more expensive models have their own built-in sensitivity check mode to ensure the sensing head is actually working. Not HC suitable! This type of leak detector is produced by such trademarks as ExTech, Fielpiece, Testo, etc.

Heated Diode leak detector (Testo, 0563 3163).jpg

Infrared detectors have an optical bench that the refrigerant passes through. The refrigerant absorbs IR radiation. The bench senses this and converts it into an alarm dependent on the amount of IR absorbed. The technology is very accurate and less prone to contamination. It has only been recently deployed in a small handheld technology but has been widely used in larger fixed environmental detectors for many years. Check with the manufacturer before using with HC’s. One of the best well-known manufacturers of IR leak detectors is Bacharach.

Infra Red IR leak detector (Fieldpiece)

Ultrasonic detectors work on sound waves emitted when gas or vacuum escapes through a small orifice (leak). The sound is well above the frequencies sensitive to the human ear. The electronics pick up these frequencies and amplify them into an audible output that we can hear. The technology is not new but has only recently become cheap enough to use in hand-held leak detectors. The notable benefit of this type of detector is it will detect any gas or vacuum leak, including nitrogen and HC refrigerants. Suitable for HC’s. This type of leak detector is offered to you by AccuTrack, Reed Instruments, Wohler, and other trusted manufacturers.

UltraSonic leak detector (AccuTrack)

An alternative that can prove very useful for locating pin holes in areas such as evaporator tube ends is either a medical stethoscope with the diaphragm removed or a length of nylon tube held close to the ear; this simply amplifies the noise source of the leak.

2. Other leak detectors:

Halide detectors were very popular for use with CFC and HCFC refrigerants. The detector was normally powered with butane and worked in a similar way to a Bunsen burner. The air was channeled into the flame via a rubber tube connected below the flame. As air with refrigerant passed through the flame the chlorine element turned the flame from normal to green through to bright blue depending on the refrigerant content of the air. Be aware that the by-products of burning refrigerants are highly toxic. DO NOT USE this type of leak detector with HFC’s or HC’s!

Uniweld PLD33V

Fluorescent (UV) detectors use an additive, which is added to the oil in a system. It travels around with the oil and can be detected using ultra-violet (UV) light where it has leaked from the system. The handheld UV kits come in various forms, typically consisting of a UV lamp, additive injection kits, and polarising goggles. The system relies on the oil leaking from the system (with additive) though in some cases, oil separators almost totally remove the additive as it leaves the pack or condensing unit rendering it useless around the remainder of the system. Almost all car manufacturers charge this additive with the refrigerant into car A/C systems, and some gas manufacturers supply refrigerant with the additive included. Suitable for HC’s. This type of leak detector is produced by such manufacturers as La-Co, Mastercool, Uniweld, etc.

Mastercool 53515

Soap & Water may be used to test for refrigerant leaks. Make soap and water solution by mixing liquid soap (washing up liquid) with water into a thick consistency. Let it stand until the bubbles have dispersed, and then apply it to the suspected leak with a soft brush. A leak will cause bubbles to appear under the soap solution. Care should be taken that a system is not in a vacuum before using this method as the solution could be drawn into the system with obvious results. Soap and water are ineffective on suction lines operation below freezing. Leak detection spray is also widely available in aerosol cans or manual pump spray guns. Suitable for HC’s.

Additionally, we can offer you some more types of the instruments, such as a microwave leak detector and a water leak detector, which can be your helpers in sustaining the safety of your home and in lowering your bills.

3. Leak Detector Maintenance

Having selected the appropriate leak detector for the job, it is important to be sure the equipment is working. Most of the electronic leak detectors need regular calibration, and the corona discharge and heated diode types require sensor changes at regular intervals. Read the manufacturers instructions as a leak detector that is not working is not obvious to the user. DO NOT open a bottle of refrigerant over your detector head to prove that it is working - even a sensor that is spent will sense that, so would you!

4. Leak Detection Technique

Having the right leak detector and checking its operation technique could mean the difference between finding a leak and missing it. We have bulleted below the main points to successful leak detection, especially when using electronic leak detectors. They are not in priority order but will all add up to successful hunting:

  • Don’t underestimate visual leak detection, look for oil traces – use your eyes;
  • Ensure you have the correct leak detector for the job, and it is operating correctly;
  • Move the electronic detector sensing tip slowly over the area being tested in a constant motion;
  • If you sense a leak, move back and forth over the area until you zero in on the leak. If you simply point the detector at a suspected leak it will zero out, and you might miss it;
  • Refrigerants are heavier than air, so it is always worth a quick swoop of the cold room floor or cabinet base. Watch out for any water or oil! It might give you a quick indicator if you are in the right area;
  • Do not trust electronics alone. If your leak detector has indicated something, use soapy water to zero in on it. Use a mix of technologies. They all work, some better than others dependent on the environment, and no technology is best!

Question And Answer