Explosion Proof in electronics means to withstand 🧨 electrolytic capacitor or arcing switch in a vacuum sealed container but basically means different grades of pressure and strength but may also mean non-arcing with combustible gas, so this may involve gas tight seals that do not allow penetration unlike Teflon seals which release H2 from sealed boxes with SLA batteries to relieve pressure during controlled charging. You can imagine an outdoor application with electronics with arc suppression and SLA battery backup for a Wireless repeater might be explosive without some venting or a Teflon seal to resist water but allow H2 to be released.
There are several design-specific criteria; Rigidity, moisture seal, explosive gas seals, arc avoidance, partial discharge from ESD externally, or Partial Discharge (PD) internally from humidity and contaminants reducing the breakdown threshold <1V/mm.
Gas Leak detectors do not imply explosion-proof
Normally even expensive home gas detectors warn you to keep gas venting batteries away for combustible gases !!,
So your requirements are vague
What spec’s do you want to meet?
The ratings for safety tradeoff the risk for Partial Discharge or ESD due to dust and static generation and the level of exposure to combustible gases.
Which gasses do you want to detect? A combustible gas leak detector may not detect toxic Carbon Monoxide as the sensors are different. To prevent a gas leak requires a solenoid before the flex hose and not after as inside the furnace, if the flex hose was damaged by impact of moving heavy equipment, the gas alarm may not prevent a leaking house from blowing up!! Although a gas leak inside a furnace may be possible detect and sound alarm and shutoff the combustible gas source.
So your specs are vague.
However, semiconductor combustible gases can detect many including any or all the following:
Alcohol Ammonia Benzene
Ethylene Oxide Gasoline-Petrol Halon
Industrial Solvents Jet Fuel
Lacquer Thinners Methane
Naphtha Natural Gas Propane Refrigerants Toluene
For Hydrogen gas vapours H2 has a lower explosive limit (LEL) of 5 % so up to 1,000 ppm or 0.1% “May” be considered the safe yet warning limit may be 10,000 ppm and >=4% with any static discharge may explode. Other gases may be more volatile. So accuracy is not uniform for all gases.
Normally “any” conformal coating will not do, for preventing flashover as most plastics are hygroscopic , although they extend the life in some harsh environments.
Even epoxy sealed plastic IC’s once failed below freezing. They eventually absorbed moisture and failed when frozen so ceramic IC’s were offered until Sumotomo’s epoxy formulation and process was developed. When Plastic IC’s first came out, they were only rated 0 to 70’C , now the improvements from Japanese R&D made it possible to cover the wider temp range.
Nylon, ABS, Acrylic, Polyurethane, Polycarbonate, PET, PBT
Polyethylene, Polypropylene, Polystyrene, PVC
Normally an explosion proof container is a rugged sand-cast aluminum case design to withstand high pressures. Better products use an epoxy coating. So moisture sealed alone is not adequate to prevent any possible explosion from an electronic failure.
If you need the best low capacitance moisture blocking conformal coating then in Aerospace they use Paralene, with vapor deposition, IC’s use special epoxy formulations and clean room procedures. The other coatings when thick enough may extend poor performance life such as silicates , acrylics and silicone but may not perform as well, if thin yet too much can cause crosstalk and capacitive loading.
The science behind explosion proof is determined by the contamination level of a good insulator degraded by moisture /and or dust where the low dielectric constant contaminant breaks down by accepting charges faster than the medium of higher dielectric content resulting in what is well known to those familiar with Partial Discharge , PD which is the precursor to an ionization Discharge or arc or dielectric breakdown of the insulation.
The test method depends on environmental stress levels of humidity and hygroscopic rates of various plastics with contaminants that may absorb moisture which has a polar dielectric constant about 20x greater than most plastics. The contaminant levels only need to be in the parts /million or PPM for PD to occur and this leakage rate with dielectric constant creates a unijunction like oscillator that may Discharge at low ratios of the expected breakdown kV/mm or V/um or mV/nm. With cycle times of many minutes, becoming more rapid with excitation ratio relative to Vbreakdown.
The test method simple using worst case ambient contamination (dust, moisture, salt spray) with a slow ramped voltage and determine the spark noise on an AM or SW radio nearby or using a scope probe shorted to its ground clip, wrapped around the conductor to detect the PD current pulse. The derating factor of stress voltages either conducted or induced to PD activity determines the safety margin after high temp/high humidity soak to accelerate moisture ingress.
The specific test procedure may vary from this, but the science of determining margin to trigger threshold is the key safety factor.
Exactly the same science is used in power transformers whether dry or oil filled and yet they only test to BDV or breakdown voltage instead of the optional test for PD. PD activity is monitored by H2 dissolved gas and yet so many transformers blow up every year that could be prevented with PD monitors and often only installed in million dollar transformers, yet it is so cheap to monitor.