Converting OELs

Occupational Exposure Limits (OELs, TLVs, PELs, etc.) are usually expressed in mg/m3. Only in instances where the substance exists as a gas or vapour at normal room temperature and pressure will you see OELs expresses in parts per million.

Many practitioners find themselves in situations which require them to convert the OEL readings from ppm to mg/m3. If you find yourself in such a situation, you may use the following formula to do the conversion quickly.

where R is the ideal gas constant; T, the temperature in  kelvins (273.16 + T°C); and P, the pressure in mm Hg.

Health concerns of lead acid batteries….

Health concerns of lead acid batteries….

One of the most remarkable and novel discoveries in the last 400 years has been electricity. The practical use of electricity has only been at our disposal since the mid-to late 1800s but has since ballooned to power almost all of our day to day industrial applications.

Batteries, or commonly known as accumulators,  as we come to see and use today are relatively safe, but precaution applies when touching damaged cells and when handling lead acid systems that have access to lead and sulfuric acid. This post will talk about lead acid (LA) batteries.

Lead Acid Batteries

LA batteries belongs to a mature, reliable and well-understood technology and when used correctly is durable and provides dependable services.

Examples of LA Batteries

Fig 1. Examples of LA batteries

Some of the advantages and disadvantages of LA batteries are summarized as below.

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Fig 2. Advantages and limitations of LA batteries

Before purchasing any LA batteries, you should insist on your copy of the Safety Data Sheet, in compliance with Globally Harmonized Standards (GHS). Before using your LA batteries, it is beneficial if users are aware about the following health hazards.

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 particulates 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 believe that Ludwig van Beethoven became ill and died because of lead poisoning.

In Singapore, the long term exposure limit of lead is 0.15 mg/m3. To convert, click here.

Sulfuric Acid

The second concern when using LA batteries is the highly corrosive sulfuric acid. Eye contact can cause permanent blindness; swallowing damages internal organs that can lead to death. First aid treatment calls for flushing the skin for 10 to 15 minutes with large amounts of water to cool the affected tissues and to prevent secondary damage. Immediately remove contaminated clothing and thoroughly wash the underlying skin. Always wear protective equipment when handling the sulfuric acid.

In Singapore, the long term exposure limit of lead is 1 mg/m3 and the short term exposure limit is 3 mg/m3. To convert, click here.

Hydrogen-Sulfide

Hydrogen sulfide is usually present during the charging of LA batteries. The gas is colorless, very poisonous, flammable and has the odor of rotten eggs. Hydrogen sulfate also occurs naturally during the breakdown of organic matter in swamps and sewers. Although noticeable at first, the sense of smell deadens with time and potential victims may be unaware of its presence. This is commonly known as ‘olfactory fatigue’. As a simple guideline, hydrogen sulfide becomes harmful to human life if the odor is noticeable.

In Singapore, the long term exposure limit of lead is 14 mg/m3 and the short term exposure limit is 21 mg/m3. To convert, click here.