Explosion-proof camera specification sheets contain two sets of data: camera performance parameters (resolution, minimum illumination, compression format) and hazardous area certification data (ATEX or NEC marking, gas group, temperature class). Both are equally important. A camera that is correctly certified but underperforms at night, or performs well optically but is certified for the wrong gas group, fails the installation in different ways.
This guide decodes each section of a typical explosion-proof camera spec sheet, explains what the numbers mean in real-world terms, and identifies the values that are most commonly misunderstood during procurement. The goal is to help engineering and procurement teams read a specification sheet as a technical document, not just a marketing checklist.
Resolution: What Megapixel Numbers Actually Mean
Resolution is specified as pixels in the format Width x Height (e.g., 1920×1080) or as megapixels (2MP = 1920×1080). Higher resolution means more detail at a given distance, or the same detail level at a greater distance. The practical significance of resolution depends entirely on the required monitoring task and the camera’s coverage angle.
A 2MP camera with a narrow 27-degree FOV (12mm lens) provides more detail per target at 50 meters than an 8MP camera with a wide 90-degree FOV at the same distance — because the 8MP camera’s pixels are spread across a much larger area. When comparing spec sheets, always evaluate resolution alongside the lens focal length and FOV. Resolution alone is meaningless without knowing what area it covers.
Minimum Illumination: What the Lux Values Mean
Minimum illumination is the lowest light level at which the camera produces a usable image. It is specified in lux (lx) for color and sometimes a separate value for black-and-white mode. Lower lux values indicate better low-light performance.
| Minimum Illumination Value | Practical Meaning | Equivalent Conditions |
|---|---|---|
| 0.5 lux (color) | Poor low-light, usable only in lit areas | Dimly lit parking area |
| 0.05 lux (color) | Good low-light for outdoor use | Facility perimeter with distant lighting |
| 0.01 lux (color) | Excellent, usable in near-dark conditions | Moonlit outdoor area |
| 0.001 lux (B&W) | Usable in starlight conditions without IR | Open area under clear starlit sky |
| 0 lux (with IR on) | Complete darkness — active IR illumination | Total blackout; IR LEDs illuminate the scene |
For hazardous area cameras without artificial lighting (such as remote tank farm perimeters), specify cameras with 0.01 lux color or better, plus built-in IR illumination. Cameras claiming “0 lux” are only usable with their IR LEDs active — they do not image a completely dark scene without the IR. Always verify the IR illumination range (30m, 50m, 100m) at the working distance required.
WDR (Wide Dynamic Range): When It Matters and When It Doesn’t
WDR allows cameras to capture usable detail in scenes with extreme contrast — bright sunlight through a dark opening, or a brightly lit process area with dark shadows. WDR is specified in decibels (dB): 60dB is basic, 100dB is good, 120dB+ is high-end. True WDR uses multiple exposures combined in hardware; digital WDR (DWDR) is software enhancement with less effective results.
In hazardous area applications, WDR is most valuable at facility entry gates (bright sky background with vehicles in shadow), offshore deck monitoring (sun reflection off the sea), and chemical loading areas where tankers create large shadows. In uniformly lit indoor process areas, WDR is less critical. Specify a minimum 100dB true WDR only where the monitoring task actually requires it — not as a blanket specification that eliminates otherwise suitable cameras.
Decoding the ATEX Marking
Every ATEX-certified camera carries a marking on the nameplate that identifies exactly what the certification covers. A typical marking reads: Ex II 2G Ex d IIB T4 Gb. Each field has a specific meaning:
Ex — certified to IEC 60079 standards (the European Ex certification prefix). II — Group II: surface industries (not underground mining, which is Group I). 2G — Category 2, Gas: approved for Zone 1 and Zone 2; remains safe with one expected fault. Ex d — Protection method: flameproof enclosure. The housing contains any internal ignition and prevents propagation to the external atmosphere. IIB — Gas group: covers IIA (propane, methane) and IIB (ethylene) gases. If the facility contains hydrogen or acetylene (Group IIC), the camera must be marked IIC, not IIB. T4 — Temperature class: maximum surface temperature 135°C. This must be lower than the auto-ignition temperature of the gases present. Gb — Equipment Protection Level b: reliable level of protection for Zone 1.
Gas group is the most commonly overlooked specification. Most petrochemical cameras are Group IIB or IIA (covering propane, methane, propylene). Facilities handling hydrogen, acetylene, or carbon disulfide require Group IIC. Installing a Group IIB camera in a Group IIC area is a compliance violation regardless of Zone rating. For a full guide to how zones and gas groups interact, see our hazardous location classification guide.
H.265 vs. H.264 Compression
Video compression format directly affects storage requirements and bandwidth. H.265 (HEVC) provides approximately 40-50% better compression than H.264 at equivalent image quality, meaning a camera recording at 1 Mbps in H.265 produces video quality roughly equivalent to 2 Mbps in H.264. For a 30-day, 16-camera system, the difference between H.264 and H.265 is approximately 20TB vs. 10TB of storage — a significant hardware cost difference.
Always specify H.265 as the minimum compression standard for new explosion-proof camera systems. Verify that the NVR or VMS can decode H.265 streams — some older VMS versions require a software upgrade for H.265 decoding. H.264 should be listed as an acceptable fallback for compatibility with legacy recording infrastructure, not as the primary specification.
Frequently Asked Questions
What resolution should I specify?
2MP for general process area monitoring. 4MP or 8MP for gate access and identification tasks. Always pair the resolution spec with the lens FOV requirement — a high-resolution camera on a wide lens provides less detail per target than a lower-resolution camera on a narrow lens.
What does T4 mean on an ATEX marking?
T4 = maximum surface temperature 135°C. Compare with the auto-ignition temperature of the gases present. If the AIT is below 135°C, a lower T-class (T5 = 100°C, T6 = 85°C) is required.
What is the difference between Group IIA, IIB, and IIC?
IIA: propane, methane (least sensitive). IIB: ethylene, H2S, common petroleum vapors. IIC: hydrogen, acetylene (most sensitive). IIC-rated cameras can go in any area; IIB cannot go in IIC areas.
What WDR rating should I look for?
100dB true WDR for high-contrast lighting applications. DWDR (digital WDR) is software-only and less effective. Don’t over-specify — 120dB WDR cameras cost significantly more and the benefit is only visible in high-contrast conditions.
H.265 or H.264?
Specify H.265 as minimum for new installations — 40-50% storage savings over H.264 at equivalent quality. Verify your VMS supports H.265 decoding before making it mandatory.
Veilux provides complete specification sheets for all camera models, including ATEX marking breakdown, performance data tested to IEC 60079 standards, and VMS compatibility lists. Request a quote and we will provide specification sheets and certificate packages for review before ordering.
Key Industry Standards and References
EPL and gas group markings are standardized in IEC 60079-0. NEC Class/Division/Group markings are in NFPA 70 Article 500. IP ratings are per IEC 60529.
Related Resources
- Explosion-Proof Camera Selection Guide
- Explosion-Proof Camera Housing Selection Guide
- IP66 vs IP67 vs IP68 Industrial Camera Ratings Explained
- ATEX Category 1, 2, 3 Equipment Guide
- Browse Explosion-Proof Cameras
- Request a Project Quote
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About the Author
Daniel Fernandez
Daniel Fernandez is a hazardous area security systems specialist with over a decade of experience specifying ATEX, IECEx, UL Class I Division 1, and cUL certified surveillance equipment for oil and gas, chemical, mining, pharmaceutical, and offshore environments. He holds expertise in NEC and IEC area classification standards and has consulted on explosion-proof camera system designs across North America, Europe, and the Middle East.