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Flying near Hydrogen Sulfide gas (flammable)

Kristina Fowler

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"Hydrogen sulfide (also known as H2S, sewer gas, swamp gas, stink damp, and sour damp) is a colorless gas known for its pungent "rotten egg" odor at low concentrations. It is extremely flammable and highly toxic."

This might sound like a silly question.... I'll be flying near an Oil & Gas facility with a known presence of Hydrogen Sulfide gas. I've heard that some O&G companies prohibit the use of drones near their assets because the drone motors may ignite flammable gas. I'd like to hear some opinions if this should be a concern. Can the drone motors actually cause the ignition of the gas? This is probably making a mountain out of a molehill but thought I'd throw it out there. I'm flying a P4P. Thanks in advance.
 
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R.Perry

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These are brushless motors so very little chance motors causing ignition. Some of the warehoused that store fertilizer (Sodium Nitrate) had electric forklifts with sealed motors and never had any problems.
You also must understand that these drones have the potential of developing a fair amount of static current that when discharged can create a spark.
 

MikeA

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I think that's a great question. Maybe in a lab someone could get it to spark off but if you are in open air I agree with @R.Perry there is no real danger. When I worked in that industry any use of a non-rated spark producing tool (even battery powered widgets like drones) required a couple extra permitting steps and checks, usually a 4 Gas sniffer to make sure you're not taking off in an H2S cloud. I would check with the safety personnel just so you are all on the same page, but I think it will fly.
 

jaja6009

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I would tend to think that for Hydrogen Sulfide the chances are good that you will not encounter it at altitude. (But see below)

Hydrogen Sulfide is heavier than air. It will stay near the ground until it disperses as all gases eventually do since they are in a high state of movement.
Next it would have to be a large amount continually leaking. H2S has a LEL Lower Explosive Limit of 4.3% by volume or 43,000 ppm. That is alot, and it would have to reach the altitude of the drone.
100 ppm (parts per million) of H2S is the IDLH (Immediately Dangerous to Life and Health). While you will not die at 100ppm, at this limit you can start to have bad effects.

If there is a concern about H2S for a drone operating at altitude, I would be more concerned about you on the ground where the H2S wants to be.

On whether a drone could ignite it? I do not know the answer, but I have never seen any sUAS rated as intrinsically safe and as stated things moving can generate a charge.

I am not familiar with Oil and Gas sites as I am in coastal New Jersey, so there could be something I am missing in regards to where the H2S is coming from in that if it is being artificially vented out and up or something.

Other than having a dedicated electrochemical H2S sensor (low cost options compared to other direct reading instruments) on the drone that could record the highest reading the sensor saw in ppm (parts per million) a very cheap way to indicate if there were concerning levels of H2S that the drone flew through would be to buy some sticky pH paper wet it with water and tape it to the legs of the drone. When it lands you can look to see if the paper changed red, meaning it encountered H2S up there. This a qualitative as in yes or no but could give you the answer in an easy way but just cant tell you how much.

I would be just as concerned with methane. It is colorless and odorless and flammable. It is lighter than air and can also asphyxiate you by displacing the atmosphere around you and therefore the oxygen.

Note: I am the hazardous materials coordinator and trainer for our fire department and we have a dedicated Hazmat Technician Level Team.
 

BigAl07

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There was a test on YT a good while back where they were intentionally trying to get a drone (DJI Inspire IIRC) to ignite a highly flammable mixture inside of a controlled container. I can't recall the channel but they could NOT get it to happen and had to introduce a sparking device to confirm the mixture was indeed flammable.

With that being said, if we are called to an Emergency Incident and a Flammable Gas is present, we are NOT allowed to put the UAS into the air unless it has been certified as Intrinsically Safe. To date we don't have such a drone and to be honest, I'm not sure if I've seen one but if there is one it is going to be CRAZY expensive.

So while the odds of the drone igniting the mixture is probably crazy low it's probably not ZERO and I doubt the risk to Life & Limb is worth the reward of the flights or the penalties if you're found to be operating negligently.
 
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jaja6009

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There was a test on YT a good while back where they were intentionally trying to get a drone (DJI Inspire IIRC) to ignite a highly flammable mixture inside of a controlled container. I can't recall the channel but they could NOT get it to happen and had to introduce a sparking device to confirm the mixture was indeed flammable.

With that being said, if we are called to an Emergency Incident and a Flammable Gas is present, we are NOT allowed to put the UAS into the air unless it has been certified as Intrinsically Safe. To date we don't have such a drone and to be honest, I'm not sure if I've seen one but if there is one it is going to be CRAZY expensive.

So while the odds of the drone igniting the mixture is probably crazy low it's probably not ZERO and I doubt the risk to Life & Limb is worth the reward of the flights or the penalties if you're found to be operating negligently.
BigAl07, I have lightly browsed some of the confined space entry drones out there and I still don't see any company even mention intrinsically safe.

We do not have any ban for the drone in hazardous materials incidents, and actually it would be used in any hazmat if we needed to be able to view a fixed container or road tanker. I would just seek guidance from the ground on their air monitoring, and then approach from upwind.
We are lucky that we just got a Matrice 300 RTK and the zoom is downright amazing.


Also OP with H2S it stinks like rotten eggs. You can't miss it. But once you smell it, olfactory fatigue sets in and you lose the ability to smell it even if it stays or increases in concentration. Moral of the story, if you smell bad eggs, leave. Find the wind for that day and keep upwind of the area you are flying. Even contact the reps at the field, I am sure they know their property well and can give definitive answers.
 

Gagey52

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Great question Kristina, this raises another question. Do you complete a risk assessment before flying? Whilst difficult to ignite in some circumstances, it’s not impossible.
Regards
 

JimD

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"Hydrogen sulfide (also known as H2S, sewer gas, swamp gas, stink damp, and sour damp) is a colorless gas known for its pungent "rotten egg" odor at low concentrations. It is extremely flammable and highly toxic."

This might sound like a silly question.... I'll be flying near an Oil & Gas facility with a known presence of Hydrogen Sulfide gas. I've heard that some O&G companies prohibit the use of drones near their assets because the drone motors may ignite flammable gas. I'd like to hear some opinions if this should be a concern. Can the drone motors actually cause the ignition of the gas? This is probably making a mountain out of a molehill but thought I'd throw it out there. I'm flying a P4P. Thanks in advance.
How close is close?
You never really said how close you’ll be
 

gajman

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OSHA defines certain environments and requires products used therecto be certified as "intrincally safe." In other words incapable ofvcreating a spark. Grain silos, petroleum plants etc. You can check with OSHA for verification. In a swamp I font thonk you have any problems, there are enough motors smoking and shooting to prove the environment safe, commercial areas are your greatest concern.
 
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KLAX

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Kristina, it's highly unlikely (but not impossible).
Risk assessments for O&G facilities are critical and must be performed before every flight. Additionally, the UAV crew should have direct communications with equipment operators to quickly react to "changing conditions" (leak develops, evacuation, unit upset, etc.) during the flight. Stuff happens.

Are you flying in an O&G facility in the U.S.?
H2S, NH3, SO2 are taken very seriously at very low concentrations. Most U.S. facilities have fixed sensors within 3 feet of the ground which will alarm at about 10ppm (H2S).

My experience with unmanned systems is almost exclusive to dense, online refining facilities with multiple flights per day.
For nearly all lower explosive limits, detection and dilution is the solution. The higher risk is with the launch/recovery area (ground level).
H2S poses more of a risk of asphyxiation vs. explosion (unless you're flying a "normally unattended facility" that is highly automated)

Mitigation of potential risk of LEL concentrations
  • keep the vehicle at a higher altitude (and in the wind column), and use a more capable camera with zoom, etc.
  • Continuous monitoring in the area with direct comms between facility ops and pilot
  • Have a plan that all crew members will follow if conditions change
Hope this helps
 

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