With colder air upon us, our risks associated with static electricity around our flammable liquids and gases INCREASES. With increased risks we need to counteract this with more attention to detail in our layers of protection against flash fires. Minor oversights that we got away with in the heat of the humid summer days may be the flaws that will create the perfect storm in the winter months. In this article I will discuss why colder weather increases our static risks and the minor details that can add up to prevent a disaster.
So why do we get shocked by the door knob after walking across the floor in our sock feet during winter time?
The generation and accumulation of static electricity is lessened in areas of high humidity. In high relative humidity situations (60 – 70% R.H or greater), a slight buildup of moisture will take place on solid surfaces thus turning nonconductors into marginal conductors. This layer of moisture can be as little as one molecule thick. With the concept that “electricity is lazy and all it wants to do is go to the ground and ly down and go to sleep”, these nonconductors becoming marginal conductors allows the charge we generate in the humid environments to go to ground much easier. In the colder environments, thus dry air, these nonconductors stay as nonconductors and allow the charge we generate to accumulate on us. It is when we reach out to grab that “grounded object” (e.g. door knob) the accumulated charge we have generated finds that easy path to ground and jumps from us to the door knob and travels the path to ground. PLEASE NOTE: there is much more going on in all of this, I am just trying to put it into terms that operators and maintenance personnel can relate to.
We are not actually generating more of a charge during the dryer air months, we just can not get rid of the charge as easily when everything around us becomes a conductor at varying degrees. So our focus should remain on our traditional safe guards for static control, but we MUST REMEMBER all those safe guards that naturally came with the hot humid days summer are NO LONGER there and thus we MUST ENSURE the engineered safeguards are functioning and being used properly.
Humidity is not, however, a recommended method of static control in many working environments. The issues with humidity as a means of static control can be:
- Humidity is only effective as a means of controlling static in very high relative humidity situations, typically 60 percent to 70 percent. This is not a comfortable environment for people to work in;
- Humidity has no effect on liquids;
- Certain polymeric materials, i.e., Teflon®, polyolefins, etc., are not affected by humidity;
- Heated surfaces, such as motors, machinery, conveyors, etc., are not affected by humidity because moisture cannot accumulate on these surfaces;
- In winter months, especially in cold climates, it is extremely difficult to add enough moisture to ambient air in factories to get the relative humidity up to the point where it will affect static accumulation.
PLEASE refer to my previous article on Flammable Liquids and Static Electricity in the “Safety Info Posts” section of the website.