What is H2S- Creation, Detection, and Removal in Industries

Detection of H2S

Because hydrogen sulfide is heavier than air, it can move on the ground. It accumulates in low-lying and confined, poorly ventilated spaces including basements, manholes, sewage lines, underground telephone vaults, and manure pits, thus making it easy to detect initially.

Detecting trace content of H2S can be done by using suitable methods like air monitoring equipment such as

• hydrogen sulfide detector tubes
• multi-gas meter that detect the gas

The use of proper equipment can be better for recognizing dangers, monitoring, and accessing restricted places when working in confined spaces, rather than relying on manual methods.

H2S monitoring measurement techniques

Pulsed UV fluorescence, lead acetate tape technique, semiconductor, and electrochemistry are all methods for detecting hydrogen sulfide in the atmosphere.

Pulsed ultraviolet fluorescence

The UV fluorescence principle-based H2S monitor is based on the emission of a distinctive fluorescence when SO2 molecules are exposed to UV light. The H2S meter collects an air sample in two ways. One-half of the sample is sent through the converter, where the H2S gas is catalyzed into SO2 via a catalytic process, while the other part is bypassed.

When SO2 is subjected to a beam of UV light in the 190-230 nm range, it becomes excited and generates characteristic fluorescence radiation in the 320-380 nm range when it returns to its ground state. The radiation goes through a filter and is recorded by the detector (photomultiplier tube). The concentration of H2S is the difference in signal strength between the two sections. Water vapor, nitric oxide (NO), and other hydrocarbons are also potential interferences in such hydrogen sulfide detectors.

Method of Lead Acetate Tape

This method’s H2S monitor is based on the chemical interaction of H2S with lead acetate-coated paper tape to create lead sulfide.

If H2S is present in the sensor, the color of the lead acetate tape changes because lead sulfide shows as a brown stain on the paper tape. A light source also lights the tape, and specially calibrated optics assess the H2S concentration based on tiny differences in the depth of the tape’s color shift.

Semiconductor

When a metal oxide semiconductor-based hydrogen sulfide monitor is exposed to an air sample, the H2S molecules react on the sensor’s metal oxide surface and dissociate into charged ions, causing the film’s resistance to change. This interaction is monitored as a signal and translated to the concentration of the gas. However, as compared to other H2S sensors, these consume more energy.

Electrochemical

H2S monitors work on the basis of the passage of hydrogen sulfide gas into the sensor, resulting in the formation of electrical signals proportional to the H2S concentration. As a result, it enables precise detection of even low H2S concentrations, which is critical in H2S monitoring in the ambient air.

Is Hydrogen Sulfide Dangerous

Hydrogen sulfide is a highly toxic gas. It is a colorless, odorless gas that is produced by the decomposition of organic matter. Hydrogen sulfide can be found in many industrial and commercial settings, as well as in nature.
Furthermore, hydrogen sulfide is an extremely flammable gas, and gas/air combinations can be explosive. It may travel to ignition sources and then flashback. When the gas is ignited, it burns, producing hazardous vapors and gases such as sulfur dioxide.

H2S Exposure Symptoms

H2S exposure symptoms include shock, convulsions, inability to breathe, extremely quick unconsciousness, coma, and death from high doses. Effects can occur in a matter of a few breaths, and perhaps in a single breath.

Exposure to Hydrogen Sulfide

Hydrogen sulfide exposure can occur through inhalation, skin contact, or eye contact. H2S exposure symptoms include headaches, dizziness, nausea, vomiting, and loss of consciousness. High concentrations of hydrogen sulfide can lead to death.

The general H2S exposure limit is 20 ppm. The peak limit is 50 ppm (up to 10 minutes).

There are a variety of ways to protect yourself from hydrogen sulfide exposure, including wearing proper personal protective equipment and using ventilation systems. If you believe you have been exposed to hydrogen sulfide, seek medical attention immediately.

Inhalation is the most common exposure method, and the lungs quickly absorb the gas. Wearing gas masks is very important in toxic environments.

The amount absorbed via the skin is negligible.

At low quantities of H2S in the air, people may detect the “rotten egg” stench of hydrogen sulfide.

However, with long-term low-level exposure or at high concentrations, a person loses the capacity to smell the gas, even if it is still present (olfactory fatigue).

This may happen extremely quickly, and in high quantities, the ability to smell the gas can be completely gone. As a result, DO NOT rely on your sense of smell to detect the presence of hydrogen sulfide or to warn of dangerous quantities.

Protection from H2S exposure

Before approaching regions where hydrogen sulfide may be present, take the following precautions:

• A certified person must test the air for the presence and content of hydrogen sulfide using air monitoring equipment such as hydrogen sulfide detector tubes or a multi-gas metre that detects the gas. Testing should also identify whether or not fire/explosion measures are required.
• If the gas is present, the space/area must be constantly vented to eliminate it.
• If the gas cannot be eliminated, the individual entering the space/area must wear suitable respiratory protection and any other personal protective, rescue, and communication equipment that may be required.

OSHA’s Guidelines for Confined Spaces with H2S

OSHA has very specific requirements for identifying, entering and monitoring hazardous, highly dangerous confined spaces.