Petrol Station Incident Involving Static Discharge

Initial Email Enquiry –

A security camera at a Conoco Phillips Petrol Station in Houston caught this. I guess this adds some validity to static discharge having enough energy to ignite gasoline vapours. If you live or visit the USA or other countries where latching is permitted (UK it is not) please be aware that it is very dangerous to re enter your vehicle as static build up is possible. I Noticed when she gets out of the vehicle, she does not touch anything before grabbing the nozzle. Very lucky...

Click here to view video clip.

1st Response –

I just watched the recent video from Houston of the girl having her gasoline refilling operation catch on fire. I have been wondering about something related to this. I was a firefighter for 30 years before getting into industry. I never saw or heard of a fire at a service station. We always had the locking nozzles until the self service pumps came about. When the self-service pumps came about the fire service seemed and predicated doom and gloom. It never happened. I have always been hard pressed to find any fires at self-service stations.

Now we are having them. What has changed. We also are having some diesel transports having explosions while loading at racks.

I think that the fuels have changed. I think that these clean/environmental fuels may not be conductive where old fuels were. It used be that the only fuel that we considered a static problem was JP 4 and other jet fuels. Even those fuels today are a different blend I have been told. We may have a problem with our fuels in that they do not bleed off static and that is where we are getting our ignitions. If the fuels are not conductive, that may be the problem.

The use of plastic gasoline cans could be part of the problem, but we never did have anyway to bleed off static even when we had metal cans. Just setting it on the ground or concrete I do not think bleeds off any static.

I may wrong on all of this, but something has changed. I just do not know what.

2^nd Response –

Might be we just have more vehicles on the road today so this issue becomes more common. I know here in the states there was a big push several years back for vapor recovery on the pump nozzles, this was for environmental reasons. However this is not a mandated, you cannot eliminate the static, as past articles stated types of clothing and types of auto seats. you cannot eliminate the O2, but you can eliminate the accumulation of vapor, just my two cents.

3^rd Response –

Being involved in the development of fire protective clothing we have done a lot of research on how to prevent ignition of highly flammable materials (vapours & gases) due to static discharge and hope you will find the below information useful. Unfortunately static electricity is a complex subject so please excuse the long explanation.

You mention that in former days there were probably less cases of fires at gas stations and you wonder whether or not the fuel have changed (the idea being that clean, non-conductive fuel is more hazardous in this respect than conductive fuel). This is however not the cause for this accident.

The static discharge is certainly not a result of static build-up in the fuel, but rather a static build-up in the person! In the video you can see the lady getting back into her car to get something, then comes out again and grabs the handle. Immediately the fuel vapours that have spread while the pump was running ignite. What happens is that a charge is created on the garments and body by rubbing of the clothing against the chair seat. (When getting out of the car seat, the body voltage increases tremendously to 10.000 volts or more.) When the lady touches the handle, the charge runs through the pistol to the car fuel inlet by spark discharge. The fuel vapour mixed with air is obviously highly flammable and ignites. Luckily the car itself does not explode, probably due to a lack of oxygen in the fuel tank.

How to prevent?
The question at hand is how to prevent this type of accident. The following options are available:

1. Discharge the person as quickly as possible
2. Connect the filling pistol to ground

Maximum safety will be achieved by taking both measures rather than just one.

Discharge the person
The creation of static in the body cannot be prevented as this is a natural phenomenon that cannot be avoided. There are ways however to get rid of static in the body and clothing. These need to be fast and effective enough to avoid potentially hazardous sparks.

The most widely known and effective way to discharge is to connect the person to electrical ground. As people want to walk around, the only practical way to do this is by wearing conductive shoes and standing on a conductive and grounded surface. In practice however grounding only is not sufficiently reliable:

• Most pavements and road surfaces are non-conductive when dry. In the specific case of a petrol station: many forecourts of are coated with polyurethane for environmental reasons (fuel must not leak into the environment). The PU is not conductive. Thereby the connection to ground is interrupted.
• Many soles of shoes are made of non conductive materials (Even if this person would have been wearing special conductive shoes, there would be no guarantee of an effective ground as the road surface is usually non-conductive.) For industrial use special conductive shoes are available.

The best advice to give to consumers filling their cars is therefore to touch their car before touching the handle of the hose. This eliminates any difference in voltage between the person and the car before touching the hose. Please note how the lady in the video gets out of the car without touching any metal part of her car.

In the absence of reliable grounding measures, it is best to wear garments made with Static-Control® fibers that discharge static without connection to ground through the corona effect. Corona is a safe discharge of static electricity to air. At BTTG laboratories, hydrogen explosion tests of all of our Static-Control® fabrics have been done with and without grounding, without a single ignition. Important: Grounding of the body has to be the first line of defence against static explosion!

It is important to add to this that conventional (with conductive fibers such as metal) anti-static fabrics and garments increase the risk of an incendiary spark/discharge when the body is not grounded. They are safe to use when the connection to ground is working.

Connect the filling pistol to ground. In the specific case of a petrol station it is useful to connect the metal part of the filling pistol to ground. The body charge can then flow directly to ground and not to the car.

I hope this is of use to you. Additionally I am attaching an article that I wrote for The Catalyst in 2002 which gives you more technical background about anti-static garments.

Click here to view the article (Word doc).

4^th Response –

For your information – and if you wish, action !!

Click here to view article: Gasoline Safety (PDF doc)
Click here to view article: Stadis FAQs (PDF doc)

End of email correspondence on Topic to date

Author’s identities are concealed for privacy and security reasons. Further information on the information contained in this topic can be directed to the JOIFF secretariat.