Q: Why did you decide to use IR polymers in your general purpose lens?

A. When I first started to use IR windows I used my competitors products as they were the only ones available on the market, they struck me as being very expensive and fragile, both qualities were very hard to sell to clients!! I therefore decided to investigate what other types of materials were available and what other types of manufacturing techniques could produce a very high quality, safe and efficient IR window that could be easily afforded.

As an ex Automotive testing engineer I had seen many differing types of manufacturing techniques I decided to use Plastic injection moulding as our means of manufacture, after all virtually every auxilary device on electrical switchgear is plastic and it also has the benefit of being non conductive. I then approached UL for a list of UL94 5VA flame retardant plastics and rubbers as required by the UL standard 508A which relates to Electrical Cabinets. We then carried out an extensive and rigorous testing regime on all the listed plastics and rubbers to derive the base materials that suited our requirements and also that of UL.

Once I had completed the window body design I then concentrated on the optics of the IR window, this is the most costly element of an IR window and we had to get it right. The traditional materials that were being used did have there flaws but were suitable to dry stable environments and not suited to industrial or outside applications as they were highly susceptible to thermal shock, impact and humidity, the other materials that we could use again were more expensive and would be difficult to market.

We therefore had to find a material that would first of all be able to resist the majority of environmental issues and secondly be affordable, the ideal material would be a low cost sapphire that transmits IR in the 8 – 14 micron range! Unfortunately this material does not exist so we looked for other alternatives. I had always been taught as a thermographer that IR will not transmit through plastics or glass, this is still true however there are some Polymers that do transmit IR and this is were we started looking.

I decided to use a polymer very similar to that used primarily in IR movement detectors as they were installed in vast numbers in the home and office all around the world . Our rational was that a material that was in use in vast numbers, and thus has been tried and tested in differing types of operating environments, temperatures, etc both internally and externally and would therefore be suitable to test in our application. Below is a statement by the manufacturer of the polymer we use:

Our infrared–transmitting material is also a flexible. It presently offers the least absorption loss in the 8 to 14 µm region of any of the IR polymer materials, the material is ultraviolet stabilized, and has a lifetime of many years in full sun. (In our rooftop testing facility in the full Texas sun, wind and blowing dirt tend to cause damage long before the sun does; we have yet to establish a lifetime, though material which has been on the roof for two years shows no significant UV degradation in either infrared transmittance or physical properties. We also know of at least one instance of a PIR lens array in a passive infrared motion detector that has been used outdoors in Texas for approximately 15 years without a noticeable decrease in performance.)

As you can imagine this gave me a lot of confidence in the material and it had very acceptable transmission rates in both the SW and LW infrared wavelengths, and the best thing about it all is that it was significantly cheaper than any other IR material we tested for this role. We then started our testing regime first of all with SIRA who completed the IP65 and IP2X testing, we then had the UL and ULc testing completed to 508A and 945VA and finally we have just finished our evaluation by Lloyds and now have the only type approved IR window in the world, an achivement of which we are proud.

The current range of products we now offer exceeds all of the original design requirements and our growing list of clients endorse this.

Q. Are the lenses water soluble?

A. The injection moulded plastic lens material is not water soluble. The windows employing these lenses are very durable and have an IP65 rating. Some common lens materials, however, such as Calcium Fluoride (CaF2), Magnesium Fluoride (MgF2), and Barium Fluoride (BaF2) are soluble in water and may diminish or lose their ability to transmit infrared radiation in a moist environment. (see our materials pages).

Q. Do I need a material that provides me with a visual image as well an infra red Image?

A. Our low cost windows are opaque and are therefore no good for visual images, but why do you need a visual image? The vast majority of electrical cabinets are dark inside as they do not have any internal lighting so the ability to look through the window in irrelevant as you will not be able to see anything!! However if the customer wishes to have clear windows we can suggest that you try CaF2 or BaF2 . (see our materials pages).

Q. What are the thicknesses of your lens materials?

A. Our standard crystals are 3mm thick, and the IR polymer is 0.010″.

Q. Is the IR polymer fit for use in an IR inspection Port?

A. Most definitely yes, how can it not be! The following data taken from the material safety data sheet proves the point, i.e.:

Reactivity Data

  • Polymerisation conditions to avoid = None
  • Stability = Stable
  • Conditions to Avoid = Temperatures above 325 C
  • Incompatible materials = Strong Acids, strong bases and strong oxidisers

Fire and explosion Hazards

  • Flash Point = Not Applicable
  • Auto Ignition = Not Applicable
  • Freezing Point = -107 to -135 C
  • Soluble in water = No
  • NFPA Hazard Classification (0-4) = Flammable = 1 Health = 2

Plus the IR polymer has a transmission rate of 68% at 9 microns which out performs the traditional calcium fluoride window and is flexible therefore is not as susceptible to thermal shock and fracture due to impact, consequently we and our clients believe it to be a great all round general purpose material.

Q. Is it important to have a high transmission rate?

A. All of the materials traditional used in IR windows (all of which we can supply) are listed in our materials pages. The most important thing to remember regarding IR transmission rates is that you must know what the transmission rate and wavelength that your IR window is operating in. It is irrelevant to the measurement whether it is 99% or 50%, as the camera / software will calculate the temperature based on the transmission rate that you put into the calculation, therefore you must be confident that the transmission rate is correct.

Q. What are the acual viewing diameters of you IR windows as I recently used some of your competitors IR windows and found that the acual viewing diameter was smaller than that quoted in their literature?

A. The Actual Viewing Diameters of our IR windows are:


VP-50 Series = 50mm or 2″

VP-50 Series = 75mm or 3″ VP-50 Series = 100mm or 4″

Q. What Certifications does your company and IR windows have?

A. Our Company is an ISO 9001/2000 registered company with the BSI (British Standards Institute) and was recently awarded the IIP (Investors in People) standard. Our products carry the following, we also have the distiction of controlling the whole maufacturing process.

UL & ULc

IP65 (fixed Optics) IP2X (Grills) Lloyds Type Approval Investors In People (staff management scheme) We take quality and safety very seriously as demonstrated by our constant striving to improve our services and our products, I have heard so many times that people would rather pay more for a quality product!! Who said that price reflects, this not always the case and we are living proof of the fact that through good design and a carefull choice of material wonders can be achieved, after all we have the only IR window system in the world to be type approved by Lloyds!!

What price quality and safety? take a look at our prices before you decide the answer to that question!!

Q. Is your product VPF-75 equivalent to Hawk-075-C and the H-VIR 75 COMET IR windows or not i.e. material, window and others.

A. Our VPF-75 is not an equivalent of the H-VIR 75 COMET or the Hawk IR 3″ window. The number of each of our ranges indicates the actual viewing diameter. i.e.

G M TECH VPF-75 has an actual diameter of 75mm or 3″

H-VIR 75 COMET has an actual diameter of 52mm or 2″ HAWK-075-C has a actual diameter of 67mm or 2 5/16″ (even though it is indicated a 3″ in literature!) We use UL rated plastics and gasket materials that are UL94 flame rated to 5V, we use the low cost IR1 IR material in our standard window but we can provide any material that suits your budget and operational needs. We normally suggest that new clients purchase some of our low cost units for evaluation. All the clients that have tried our new IR window systems have been delighted with the product and the results.

Q. Is the IRISS IR inspection window flame proof?

A. YES the viewport assembly and gaskets have been tested by UL to UL94 5VA, this is the highest rating that can be given to any plastic assembly, and we passed with flying colours. With regards to each optical material that we use they all have their own individual limitations, and are pointed out to the client during the consultation process. We state now and always have that the IR polymers used have a maximum temperature limitation of 100 C, even though the safety data sheet states that the ceiling temperature to be avoided is 325 C.

Our internal R&D testing of the polymers show that they do burn, however they do self extinguish and are completely constrained within the window assembly, and at the end of the tests we are able to replace the IR polymer and re-use the original gaskets etc. This is a test that none of our competitors could replicate as they only offer limited optics and they are bonded into the assembly thus the whole assembly would need to be replaced, when subjected to the same test.

Q. Why is the actual transmission rate so important?

A. All Infrared widows transmit IR energy, this is known as the transmission rate, their is not an instrument on earth that actualy measures temperature, all instruments calculate temperature and IR cameras fall into this category. IR cameras calculate tempearture using a number of variables: Distance, Emissivity, Ambient and background Temperatures and of course TRANSMISSION, when the camera has all these values imput into the thermogram it will the CALCULATE the temperature.

The graph shows how calculated temperature readings change when you vary the transmission rates. The transmission rates were changed from 99% to 50% using the same image. This gave a difference of 11.8 °C.

The significant thing to note other than the temperature difference, is that the calculated temperature increases when the transmission rate decreases, therefore if your transmission rate is too high the calculated temperature is too low!, this will cause real problems if you are using temperature as the means of categorising faults or scheduling maintenance.

Q. Is Your IR window more accurate than the competitions?

A. NO, I have seen this claim made by manufacturers and it is absolute nonsense. As the answer above demonstrates all IR cameras calculate temperature so as long as you know the transmission your calculated temperatures will be the same, regardless of which window you use.

Q. Can your IR windows be used with any IR camera?

A. The answer to this is YES. The most important thing to know is what you require, the type of equipment that you are using and the operating environment and just leave the rest to us. Our general purpose polymer window works with ALL IR CAMERA’S the only considerations that have to be given are to operating environments and the general purpose IR window fits 95% of those.

Q. Can you survey electrical equipment by just looking at the enclosure temperatures with an infrared camera?

A. You cannot obtain adequate or reliable information with an infrared camera without looking at the actual electrical components. The majority of thermographic cameras are based on digital camera technology and therefore requires a direct-line-of-site to record an accurate image. Surveys are hampered by cabinet designs that obscure the target components being imaged and thermographers are put at risk by having to open cabinets or doors in an attempt to gain access to the internal components that they wish to image, even the most comprehensive risk assessments and method statements cannot avoid the obvious risks involved.

The use of Infrared Inspection ports is becoming more common place, in fact electrical panel manufacturers are now fitting Infrared inspection ports, grills, mesh screens, etc. in an attempt to make their panels infrared friendly.

Q. What are the minimum dialectric clearances?

A. The most important area of concern is the maximum safe distance between the IR window and any live components; this is called the “dielectric clearance”. The recommended minimum dielectric clearances are as follows:

5 Kv Equipment -no less than 4 inches !! 15 Kv Equipment -no less than 6 inches !! It must be noted that under no circumstances can the minimum clearances be compromised.

Another important point to remember is that most IR cameras can not focus closer that 4″.

Q. What is the effect of using infrared windows on certified enclosures?

A. If the panel that you intend to fit the IR window into carries any certification marks then these should where reasonably practicable not be breached in any way. In the case of a panel with UL certification, you should only consider using UL recognized components; a question that is regularly asked is how does field installation of IR windows affect the UL status of the panel?

The component (in this case, IR window) can be field or factory installed. The issue is the listing of the product in the field to which it is installed. Installing this product in the field does not negate the listing mark. Customers often modify assemblies that are UL listed and marked. Any modification done in the field is not covered by an existing UL mark. Therefore, UL is not responsible for the certification of these listings.

When changes are made to listed assemblies that affect the rating of the equipment, UL will do a field inspection of the modified product to re-certify the equipment meets UL requirements. A customer may request this to be done. The IR window would have to be added to the UL procedure for that piece of equipment. If it is not covered in the UL procedure then UL could not re-certify.

In cases where the IR window is not part of a product’s UL listing, there is another option, the field evaluation by UL. Since the IR window is a UL recognized component, UL should be able to provide a UL mark that would verify the modified product had been evaluated. However this would probably not be required in most cases.

Q. Are custom materials or sizes available?

A. Custom window sizes, design, and materials are available, however the prices will vary depending on the material, specifications, and possible the number of units ordered. You must be aware that when adopting this approach the IR window is not tested or certified to any recognized standard and local approval must be gained to certify their use.

Q. Do we have to have a crystal or can we use a grill?

A. Where there is no risk to the operator of electric shock or flash over, a viewing port with no crystal but with an inner protective grill may be installed to protect the assembly from objects falling into the component during inspection but still allow full access for an image to be taken.

However you must ensure that all grills have a maximum diameter of 12mm (IP2X) and you should also be aware that the use of grills still requires the use of full personal protective equipment as they are not compliant with NFPA 70E as the thermographer is still exposed to energised components within the panel being inspected.

  • NFPA 70E
  • IP2X
Q. What effect do the windows have on the thermal image?

A. The lens material’s ability to absorb some of the infrared radiation will lower the perceived temperatures somewhat. This can be accounted for with a simple procedure or by adjusting the transmissivity setting on your camera or software. The clarity of the image will not be affected.

Q. Can we have one lens and use it in all of our windows as we go?

A. Where there is no immediate risk to the operator of electric shock, he or she may use a view port with a removable crystal option, resulting in significant savings as only one crystal will be required regardless of how many viewing ports they may have. This also allows you to use viewing crystals such as coated ZnSe which has a 99% transmission rate from 4-14 microns. ZnSe is too expensive to use in large quantities, but because you only require one crystal with the IRISS you can take advantage of the best IR viewing crystals on the market, together with the additional benefits that using them brings, at a fraction of the cost. The VPLC-50 lens carrier includes a lens and lens housing. This assembly fits into the VPR-50 windows. Both a VPLC-50 lens and VPR-50 windows are required to use the removable lens system.

However once again the use of a removable lens system is not NFPA 70E or IP2x compliant, and should you decide to use this system full precautions must be taken regarding the correct level of personal protective equipment.

  • NFPA 70E
  • IP2X
Q. Who can install and service an IR window?

A. The IR window must be installed and serviced only by qualified electrical personnel, more information regarding installation can be found in this website.

Q. How long is the warranty on your IR windows

A. Our general purpose IR windows using the IR polymer are guaranteed for the life of the panel in which they are fitted, they are not guaranteed against damage or mis-use. As our IR windows do not use any adhesives in manufacture or installation our products can be moved or upgraded with ease, We do not however give a warranty on any of the Fluoride crystals as they are hygroscopic and fragile, therefore they will fail eventually.

Q. What materials do you use in the construction of your IR windows?

A. The Bodies and gaskets of our IR windows are constructed from flame retardant plastics and rubbers, with regards to the lens materials a full list can be found in our Materials pages on this website.

Q. What does IP65 and IP2X mean?

A. IP65 and IP2X are integrity proofing test against agreed standards. IP65 relates to a NEMA 4 classification, a copy of the full report can be downloaded from this website.

  • SIRA IP Test Report
  • NEMA Standards
Q. Can I install IR windows into our field installations?

A. There are many issues to be considered when it comes to the field installation of IR windows. The first point of call should be to the manufacturers of the equipment to discuss any associated risks and produce a risk assessment and method statement covering all the requirements of the installation, you should then contact any relevant certification bodies regarding the install procedure, fitting instructions and certifications of our IR windows. Remember that under no circumstances can you impair the integrity of the panel in which you intend installing IR widows.

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In the case of UL I have attached a copy of a letter that we received from them outlining that during the testing of our IR windows that consideration was given to their suitability for field installation when installed following our installation instructions.

UL Letter re: Field Installation

Q. What is the Arc Flash rating of your IR window?

A. No IR window or individual component can ever be Arc Rated or can protect you from Arc Flash, Arc flash has the potential to produce a shock blast of up to 700 miles per hour with a core temperature of 15,000 C, and there are no materials that can resist that type of temperature and force (See Video). Panel assemblies are designed to contain and survive differing levels of arc flash energy.

There are industry standards designed to test panels for resistance to Arc Flash. If these assemblies are tested with IR viewing ports fitted, and pass the test, the standard is awarded to the assembly only, this does not mean that the IR window or any other components are Arc rated for any other assembly.

Each assembly needs to be dealt with in a case by case scenario and comprehensive risk assessments completed.

Q. What are the benefits of fitting IR windows?

A. To a thermographer there are many benefits to using IR windows, direct temperature readings will always be the preferred medium for gathering information especially on critical plant and services. IR windows are an asset to any inspection program and remove the necessity of:

  • Complex risk assessments and method statements prior to an “open panel” inspection.
  • Opening panels and exposing manpower to potentially hazardous live components.
  • Permits to isolate and shutdown panels.
  • Restarting plant after shutdown.

The additional benefits of using of IR windows are:

  • Improved thermographic survey results, as they are direct temperature measurements.
  • Improved plant reliability.
  • Safer working environment for thermographers.
  • Reduces the amount of time and costs involved in a thermographic survey, as no shutdowns are required. .
  • IR windows make our work safer, faster and more accurate, but only when installed and used correctly. If careful consideration is not given to the issues discussed in this paper the inspection port will give inaccurate results leading to poor diagnosis, thus negating the reason for fitting them in the first place.
Q.Why do I need bigger Infrared windows?

A. We have produced a paper outlining all the factors that need to be considered regarding this very subject. Why do I need bigger IR windows.

Q. How Can I measure the transmission rate of an infrared window?

A. It must be noted that specialised instrumentation is used to measure the spectral transmittance of IR window materials, however as the majority of thermographers are unable to access this type of instrumentation we have to derive methods of using our IR cameras to calculate the approximate transmission rates. I have used this method in the field many times and it has proven to be accurate and reliable, we call it the “coffee cup test”

Method 1: IR camera with external optics transmission compensation:

  1. Using electrical tape mark a low emissivity target onto a coffee cup and fill the cup with hot coffee.
  2. Set the transmission rate to 0.99 and the emissivity to 0.95.
  3. Measure the temperature of the emissivity target on the coffee cup.
  4. Place window in front of target.
  5. Calculate the IR window transmission by adjusting the camera transmission rate until the temperature reads the same as the temperature without the IR window.
  6. Mark transmission rates on IR windows.

Method 2: IR camera does not have external optics transmittance compensation.

  1. Using electrical tape mark a low emissivity target onto a coffee cup and fill the cup with hot coffee.
  2. Set IR camera emissivity to 1.
  3. Measure target apparent temperature without window in place.
  4. Place window in front of target.
  5. Adjust target emissivity until same apparent target temperature without window is found.
  6. When using IR windows in this mode, enter the product of the target emissivity times the window transmittance for emissivity in your IR camera.
  7. Mark the calculated emissivity setting on the IR window labels and ensure that all personnel using this calculation fully understand the procedure used.
  8. The major caveat here is that the target reflected apparent temperature, the window reflected apparent temperature, and the window temperature must all be equal.


This is a very popular method in use in the field today, particularly as the majority of IR cameras do not have the ability to adjust the optics transmission onboard the actual camera, but do however allow you to adjust the emissivity to obtain fairly accurate results using this methodology.

Method 3: Using IR camera reporting software:

  1. Using electrical tape mark a low emissivity target onto a coffee cup and fill the cup with hot coffee.
  2. Set the transmission rate to 0.99 and the emissivity to 0.95.
  3. Take an image of the coffee cup measuring the temperature at the emissivity target.
  4. Place window in front of target.
  5. Take an image of the coffee cup through the IR window measuring the temperature at the emissivity target.
  6. Save both images into your reporting software
  7. Calculate the IR window transmission by adjusting the transmission rate within the reporting software on the image taken through the IR window until the temperatures read the same as the image without the IR window.
  8. Mark transmission rates on IR windows.