We have a customer interested in installing access points in track service bays etc. for their wireless diagnostics systems. (laptops with wireless cards)
They've asked the question - is wireless safe round the fuel, oil etc?
Could the kit cause a static, sparks etc? I suppose, similar to what we're told about switching off mobiles in petrol station forecourts - although people do say this is an urban legend.
Does anyone know of any sites/docs that would be useful to quote to reassure?
Access points we'd use would be Cisco Aironet 1231G, with DC Injectors (located out of harms way, in comms cabinet).
If you are talking about a normal Truck repair workshop then there would be no problems, the RF on a wireless card is very low. If you are in a refinary or tanker terminal for petrol or gas then the Petrolium Regulations come into force and they are very strict. The 'no wireless' on forecourts comes from the higher powered communication transmitters which could put out a lot more power, and could theoretically cause a spark . You can get special radios that are Intrinsically safe for use in Volatile areas, mines, explosives, fuel and gas etc. Mobile phones only put out miliwatts so should not be a problem. but I will let you test that out first! ;~)
Unless there are legal requirement for intrinsically safe hardware, or the owner has some reason to believe that there are explosive fumes that'll build up, you shouldn't have a problem.
Yes. The wireless part is sufficiently low power that there will not be a spark.
It's urban legend. In the bad olde daze of tube (valve) mobile radios, the high voltage power supplies consisted of dynamotors (a type of motor generator) and vibrator (relay switcher) type power supplies. These generated real and visible sparks which could easily set off a vapor explosion. In addition, the old tube radios were mounted in the trunk of the vehicle, with no vapor seal from the gas tank, which made the trunk into a perfect confined area. I had a small explosion in the trunk of my 1960 Ford Falcon from exactly this situation.
A bit later, the dynamotors and vibrators were replace by transistor driven switchers, but the T/R relays were still wide open and generated sparks. Eventually, the T/R relays were replaced by solid state T/R switches and the RF switches by sealed reed relays. That eliminated all obvious sources of sparking. However, tradition is difficult to fight, so the warnings about turning off the radios remain. "Better safe than understanding."
I couldn't find anything specific. Maybe later. Avoid anything about "intrinsically safe" unless you're working inside a gasoline storage tank. Sparking is described by Paschen's Law:
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's_lawThis is the minimum voltage and power required to generate an arc at a specified gas pressure. At low powers and voltages, there's no real danger.
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Duh... Found my own posting on the same topic.
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The real danger is the 48VDC PoE power supply generating sparks when plugged and unplugged. This is a rather uncommon event and should not be a consideration. In addition, the PoE specification has provisions for not applying full power until after the requisite data handshake. During the handshake, there's not enough power applied to generate a spark. PoE will not deliver power into a short circuit. Not a problem.
It's still urban legend. There are any number of things in a car that could create sparks - most cars have fans that run independent of the ignition setting these days, I'd bet those have a better chance of creating a spark at the gas pumps.
True. However, the motors are fairly well enclosed. For example, the mine safety people have been using vibrating pagers in mines for many years to send text message warnings of fire, gas, etc. They use the vibrators because of the high noise level in the mines.
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(There is quite a bit here)
I vaguely recall it became an issue with pagers in the 1980's. There was a demonstration with a gallon plastic pickle jar, a few drops of gasoline, and a pager. The vibrator motor sparking allegedly caused the gasoline vapor to explode. A friend of mine tried to dupllicate the effect with several Motorola Bravo pagers, and never could get it to do anything. He eventually fired off a spark inside the plastic jar with a big inductor, which verified that the atmosphere was indeed explosive. I have the videos of all this buried somewhere.
This should probably be tested by Myth Busters. Oh, it already has been. The "Cell Phones and Gas Stations" episode.
Thanks to low power designs, current limiting batteries, and elastometric switches, pagers are easy to qualify as intrinsically safe. It's rather difficult for them to generate a spark. The one's that were used for the test were early Motorola Bravo pagers. Motorola has had a wide range of pagers under the Bravo name. (Bravo, Bravo Plus, Bravo Classic, Bravo LX, FLX, etc).
I'm not too familar with mine communications. After every mine disaster, there's usually a legislative push to require PED's (personal emergency devices), of one sort or other, in the mines. Some of these devices are two-way pagers, which record the last known position of the miner. Others are integrated with lights, intercoms, sniffers, 2way radios, etc. See: |
No. There wasn't enough gasoline to do any damage. It's quite an impressive demonstration of what a few drops of gasoline can do inside a gallon plastic container. I'll spare you the math[1]. The optimum range for an explosion is about 3% vapor. If you need some entertainment, arrange a spark gap inside a gallon container (plastic, not glass, pickle jar), add a few drops of gasoline, and apply a suitable spark. A spark plug, battery, and a big inductor will do the trick. You will have trouble hearing after the explosion. When we were playing around, we found that *ONE* drop of gasoline in a gallon jar was sufficient to make a loud bang, and three were required to blow the metal lid off the jar.
Were you planning on protesting the higher gasoline prices? Talking on your cell phone in a gas station is not the answer.
[1] Start with 40,000 Joules/gram or 40,000 watt-seconds/gram or 10 about Calories/gram.
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