Safety when CHARGING your Vehicle Battery H2S is Near!

One mother in the USA in her car she was sitting on a H2S time bomb, and she and her little daughter perished while driving, why you ask! The charging of lead-acid batteries can be hazardous. However, many workers may not see it that way since it is such a common activity in many workplaces. The two primary risks are from hydrogen gas formed when the battery is being charged and the sulfuric acid in the battery fluid.

Health Concerns with Batteries

Batteries are safe, but caution is necessary when touching damaged cells and when handling lead acid systems that have access to lead and sulfuric acid. Several countries label lead acid as hazardous material, and rightly so. Lead can be a health hazard if not properly handled.  The sulfuric acid in a lead acid battery is highly corrosive and is more harmful thanacids used in most other battery systems. Contact with eye can cause permanent blindness; swallowing damages internal organs that can lead to death.

Sulfuric acid is a very strong chemical that is corrosive. Corrosive means it can cause severe burns and tissue damage when it comes into contact with the skin or mucous membranes. This article discusses poisoning from sulfuric acid.

These materials include acid, lead, nickel, lithium, cadmium, alkaline, mercury and nickel metal hydride. When batteries are not properly disposed of the casing can disintegrate and the toxic chemicals within can leach into the surrounding environment.

Gases produced or released by the batteries while they are being charged can be a significant safety concern, especially when the batteries are located or charged in an enclosed or poorly ventilated area, or on the company or personal vehicles. Over-charging a lead acid battery can produce hydrogen-sulfide. The gas is colorless, very poisonous, flammable and has the odor of rotten eggs. Lead acid batteries are used to power forklifts, carts and many other types of machinery in many industrial settings. Many facilities have charging areas where multiple heavy duty lead acid batteries are recharged at the same time. In some cases facilities maintain large banks of lead acid batteries that are used to provide backup power to critical systems during an emergency.

Hydrogen sulfate also occurs naturally during the breakdown of organic matter in swamps and sewers; it is also present in volcanic gases, natural gas, and some well waters. Being heavier than air, the gas accumulates at the bottom of poorly ventilated spaces. Although noticeable at first, the sense of smell deadens with time and potential victims may be unaware of its presence.  It's comparable in toxicity to hydrogen cyanide. 

 Anything with a sulfide component can break down into H2S, along with anything that is organic can also break down into H2S.  While anything with a sulfide can break down to form H2S, a lead acid battery contains sulfate in the form of sulfuric acid. It is energetically very unfavorable to go from that to a sulfide and pretty much has to be enzymatic. Even then, any H2S produced should react with the sulfuric acid in the battery. 

What gets me though is first responders reported a strong odor, at concentrations of 100-150 ppm you lose your sense of smell, before that you'd suffer from drowsiness after 15-30 minutes of exposure so they'd have to be driving for a while with dizziness, drowsiness eye irritation and load of other things.

Lead

Lead is a toxic metal that can enter the body by inhalation of lead dust or ingestion when touching the mouth with lead-contaminated hands. If leaked onto the ground, acid and lead particles contaminate the soil and become airborne when dry. Children and fetuses of pregnant women are most vulnerable to lead exposure because their bodies are developing. Excessive levels of lead can affect a child’s growth, cause brain damage, harm kidneys, impair hearing and induce behavioral problems. In adults, lead can cause memory loss and lower the ability to concentrate, as well as harm the reproductive system. Lead is also known to cause high blood pressure, nerve disorders, and muscle and joint pain. Researchers speculate that Ludwig van Beethoven became ill and died because of lead poisoning. 

By 2017, members of the International Lead Association (ILA) want to keep the lead blood level of workers in mining, smelting, refining and recycling below 30 micrograms per deciliter (30μg/dl). 

Sulfuric Acid

The sulfuric acid in a lead acid battery is highly corrosive and is more harmful than acids used in most other battery systems. Contact with eye can cause permanent blindness; swallowing damages internal organs that can lead to death. First aid treatment calls for flushing the skin for 10–15 minutes with large amounts of water to cool the affected tissue and to prevent secondary damage. Immediately remove contaminated clothing and thoroughly wash the underlying skin. Always wear protective equipment when handling sulfuric acid.

Even though sulfuric acid contains sulfur, hydrogen sulfide (H2S) is not normally associated with charging or discharging lead acid batteries that contain sulfuric acid. Whatever you smelled, it was probably not H2S due to the problems you ran into charging your batteries.

Car batteries produce electricity through an electro-chemical reaction. In lead acid car batteries, electricity is produced as ions flow from the lead oxide anode to the metallic lead cathode, through an electrolyte mixture of sulphuric acid and water. If you apply a current, it reverses the reaction and the battery gets recharged.

Even if your car is parked and you’re not using the battery, the reaction keeps happening and it will slowly lose its charge.

Add the power drain from a bunch of accessories - like the alarm system and even the memory settings for the radio, seats and climate control system - and a battery could be completely drained in weeks if nobody is regularly driving the car to recharge it.

So where does the hydrogen gas come in?

There’s hydrogen in that electrolyte mixture, and normally it mostly stays there. Unless it’s exposed to a lot of heat, say, from overcharging with a traditional charger - or from having booster cables installed backwards, P bar Y Safety says. â€œIf a battery is charged at a high charging rate or is being overcharged, the electrolyte will start to release the hydrogen - since released hydrogen is flammable, if a spark is provided it can explode.”

Then you get hydrogen sulphide gas - which is poisonous, flammable and smells like rotten eggs.

The most important reaction byproducts associated with sulfuric acid (H2SO4) are hydrogen and sulfur dioxide. Overcharging, or lead acid battery malfunctions can produce hydrogen. In fact, if you look, there is almost always at least a little H2 around in areas where lead batteries are being charged.

Sulfuric acid reacts with a number of metals and substances to produce SO2 as well as other “sulfur oxides” (SOx) such as SO3, SO4, S2O, etc.). Many sulfur oxides have a pungent odor, but they are NOT H2S. H2S is a reduced sulfide, not an oxide. When you have a spill, SO2 is generally the most important gaseous reaction by-product.

During discharge of a lead acid battery you have the following two half-cell reactions. H2S is NOT on the list of byproducts, either from normal or catastrophic discharge!

Negative plate reaction:

Pb (solid) + HSO4– (aqueous) → PbSO4 (solid) + H+ (aqueous) + 2e?

Positive plate reaction:

PbO2 (solid) + HSO4– (aqueous) + 3H+ (aqueous) + 2e? â†’ PbSO4 (solid) + 2H2O

The total reaction can be written as:

Pb (solid) + PbO2 (solid) + 2H2SO4 (aqueous) → 2PbSO4 (solid) + 2H2O

During charging, (especially in the event of overcharging), lead acid batteries produce oxygen and hydrogen. These gases are produced by the electrolysis of water from the aqueous solution of sulfuric acid. Since the water is lost, the electrolyte can be depleted. This is why you need to add water to non-sealed lead acid batteries. When a lead acid battery cell “blows” or becomes incapable of being charged properly, the amount of hydrogen produced can increase catastrophically:

Water is oxidized at the negative anode: 2 H2O (liquid) → O2 (gas) + 4 H+ (aqueous) + 4e?

The protons (H+) produced at the anode are reduced at the positive cathode: 2 H+ (aqueous) + 2e? â†’ H2

So, in an area where lead acid batteries are being charged, what you primarily need to measure is H2.

Hydrogen is not toxic, but at high concentrations is a highly explosive gas. The 100% LEL concentration for hydrogen is 4.0% by volume. At this concentration, all it takes is a source of ignition to cause an explosion. Sparking from a battery terminal as it is connected or disconnected from the charging system is more than adequate as a source of ignition energy. That’s why lead acid batteries should only be charged in well ventilated areas.

The best way to measure hydrogen in an area where you are charging batteries is with a permanently installed monitoring system. You can use a standard catalytic LEL sensor, or you can measure the hydrogen by means of a substance specific electrochemical sensor. The sensor and housing need to be designed and certified for installation and use in hazardous locations characterized by the potential presence of combustible gas. Since hydrogen is lighter than air, H2 sensors are usually mounted to the wall or ceiling at a height at least slightly above the source of gas.

Readings from the H2 sensors can displayed right where the sensor is located, or on a remotely located controller or monitor.  Readings from the sensors can be used to activate relays, fans or alarms, or the information can be transmitted and integrated into the facility’s overall environmental health and safety and fire detection systems.

For LEL range measurement, using a standard catalytic combustible gas (CC) sensor with a range of 0 – 100% LEL is a good approach. For situations where you need to take action at a lower concentration, using an electrochemical (EC) toxic gas sensor to measure the hydrogen may be a better approach. The typical range for an EC hydrogen sensor is 0 – 2,000 ppm. (This is equivalent to a range of 1.0 – 5.0% LEL.)

In the event of a sulfuric acid spill, or where the sulfuric acid is coming into contact with metals and / or other materials, you may need to measure SO2 as well. Although this is normally not necessary in charging areas where the acid is fully contained in the batteries.

If you are concerned with aerosol droplets of sulfuric acid, you can directly measure H2SO4 as well. Once again, this is not normally a concern in battery charging areas.

"Hydrogen sulfide is a colorless gas with a rotten-egg odor. Some people can smell hydrogen sulfide at very low levels, as low as 0.5 parts per billion (ppb) in air. Most hydrogen sulfide in the air comes from natural sources. It is produced when bacteria break down plant and animal material, often in stagnant waters with low oxygen content such as bogs and swamps. Volcanoes, hot springs and underwater thermal vents also release hydrogen sulfide. Industrial sources of hydrogen sulfide include petroleum and natural gas extraction and refining, pulp and paper manufacturing, rayon textile production, chemical manufacturing and waste disposal. Some bacteria change calcium sulfate, the major component of wallboard, into hydrogen sulfide. If construction and demolition debris contain large quantities of wallboard, large amounts of hydrogen sulfide can be formed. Production is greatest when the wallboard is finely crushed and when there is little oxygen, such as when the debris is buried and soaked with water. 

Most of the information on human health effects from hydrogen sulfide exposure comes from accidental and industrial exposures to high levels. Exposure to high levels can cause muscle cramps, low blood pressure, slow respiration and loss of consciousness. Short-term exposure to moderate amounts of hydrogen sulfide in the workplace produces eye, nose and throat irritation, nausea, dizziness, breathing difficulties, headaches and loss of appetite and sleep. Continued exposure can irritate the respiratory passages and can lead to a buildup of fluid in the lungs. 

Human volunteers have been exposed to hydrogen sulfide for up to thirty minutes during moderate exercise at levels equal to or half the (OH&S) 8-hour standard (10,000 ppb). Chemical changes in blood and muscle were observed, but no volunteer experienced adverse symptoms and no changes were seen in lung function measurements. 

There is limited information on the effects of long-term exposure to low levels of hydrogen sulfide. People working in industries where hydrogen sulfide exposure is common, but is usually below the OH&S 8-hour standard (10,000 ppb), may have decreased lung function and increased risk of spontaneous abortion and impaired neurological functions (including reaction time, balance, color discrimination, short-term memory and mood) compared to unexposed workers. People living near industries that emit hydrogen sulfide have an increased risk of eye irritation, cough, headache, nasal blockage and impaired neurological function (same measures as above) compared to unexposed residents. Limited information is available about exposure levels in studies of people working in or living near industries emitting hydrogen sulfide. Hydrogen sulfide exposure is assumed in these studies based on job title, work history or living near facilities emitting hydrogen sulfide. In all cases, the people with presumed hydrogen sulfide exposure had or likely had exposures to other chemicals that could have contributed to some health effects. 

Foul odors and health effects were investigated in an Indiana community near a waste disposal lagoon and in five New York State communities near landfills containing construction and demolition debris. Hydrogen sulfide levels in the Indiana community ranged up to 300 ppb during a two-month period. Levels in two of the New York communities ranged up to 4000 ppb for periods of several months. During these episodes there were frequent health complaints including eye, throat and lung irritation, nausea, headache, nasal blockage, sleeping difficulties, weight loss, chest pain, and asthma attacks. Although other chemicals may have been present in the air, these effects are consistent with those of hydrogen sulfide. 

The main effects of short-term and long-term hydrogen sulfide exposure in laboratory animals are nasal and lung irritation and damage and effects on the brain. These effects are consistent with effects seen in people exposed to hydrogen sulfide."