Monitoring H2S, Ammonia, Mercaptans and VOCs Around Industrial Sites
This guide explains how to monitor H2S, ammonia and mercaptans at industrial sites in Saudi Arabia, with VOC measurements alongside. Industrial odour is rarely one universal pollutant. Wastewater and sour-gas sources may involve hydrogen sulfide. Fertiliser, rendering or biological processes may involve ammonia. Refineries, gas handling and some waste processes can involve mercaptans and other reduced-sulfur compounds. Solvents, fuels, coatings and process streams can release mixtures of volatile organic compounds. Monitoring should follow the credible source and decision, not a generic “odour sensor” label.
Odour, worker safety and environmental compliance are also different questions. A compound may be smelled below an occupational concern, while some hazardous conditions cannot be judged reliably by smell. The applicable safety, permit and client requirements determine the method and action level.
We support gas-monitoring selection and configured monitoring programmes across Saudi Arabia. You receive a written proposal setting out the configuration, scope, lead time and price. Request a quotation
H2S monitoring: useful indicator, serious hazard
H2S is associated with sewer networks, wastewater processes, anaerobic conditions, sour hydrocarbons and some industrial sulfur streams. A targeted sensor can provide continuous timing, show changes among locations and support comparison with pressure, wind or operating events.
Smell must never be used as the safety monitor. NIOSH states that olfactory fatigue can occur rapidly during continuous exposure. Environmental odour stations and handheld diagnostic instruments are not automatically approved personal or confined-space monitors. Specify the range and purpose separately for community-level trends, process diagnostics and occupational safety.
How to monitor H2S, ammonia and mercaptans: sources and conditions
Ammonia may be relevant around fertiliser handling, refrigeration, livestock or organic-waste processes, wastewater and some chemical operations. It is highly soluble and its behaviour is influenced by moisture and process conditions. A sensor selection should consider expected range, temperature, humidity, cross-sensitivity, response and recovery.
An ammonia reading can support an odour investigation when the source chemistry makes sense. It does not quantify overall odour from mixtures, and a general “nitrogen” or total-VOC channel cannot be substituted for a specific NH3 result.
Mercaptans and reduced-sulfur compounds
Mercaptans, also called thiols, include strongly odorous sulfur compounds such as methanethiol. Potential sources include gas odorisation, refining and petrochemical streams, pulp processes, wastewater and decomposing organic matter. Different sulfur compounds can have different sensor responses and analytical requirements.
A broad reduced-sulfur or total-VOC response may flag change but may not distinguish H2S from a mercaptan or identify which thiol is present. NIOSH lists methanethiol as a distinct chemical with its own properties and measurement methods. When identity matters, the project may require selective instruments, treated sampling and compound-specific laboratory analysis through VOC and sulfur analytical coordination.
VOC and total-VOC are not the same as speciation
VOC describes a large class, not one compound. A PID-based total-VOC reading responds to many ionisable vapours with different sensitivities and may not respond well to others. Calibration gas and correction assumptions affect the reported equivalent concentration. The signal is valuable for trends, screening and event timing, but it does not reveal the full mixture.
BTEX or another named compound requires a method capable of identifying and quantifying that compound. Sample media, pumps, holding times and laboratory techniques should be chosen for the target list. The VOC, BTEX and speciated-gas diagnostics page separates live indicators from qualified analytical confirmation.
Choose instruments from the source hypothesis
Build a table of source, target compound, normal and event range, required response time, potential interferents, environmental conditions and action. Fixed monitoring is useful for continuous visibility at repeat locations. Portable instruments can follow an event or compare a route. Passive or active samples can support compound-specific analysis. Odour bags and dynamic olfactometry address sensory concentration, not chemical speciation.
Place instruments around the intended question rather than the easiest power point. Source-proximate locations can reveal operating events; boundary or receptor points address transport and impact; an upwind or context point helps interpret incoming conditions. Inlets should avoid local exhausts, walls and obstructions unless that microenvironment is deliberately being tested. Changing wind means one nominally downwind point may not remain representative.
Ranges and averaging intervals should reflect both the expected background and the event. A high-range safety sensor may not resolve low environmental changes, while a low-range channel may overload close to a source. Where more than one range or method is needed, label its purpose clearly in the data system.
For oil, gas and petrochemical settings, link the table to process knowledge and the oil, gas, refinery and petrochemical odour/VOC application. Weather and operational logs are necessary for interpretation. A concentration rise plus a wind direction can narrow an investigation, but it does not automatically prove the source.
Build a quality and response plan
Confirm calibration gas, zero checks, sensor life, inlet maintenance, humidity and temperature handling, data-status flags and cross-sensitivity documentation. Collocate or compare instruments when the decision requires local performance evidence. Record firmware and sensor replacements so response changes are traceable.
Alarm rules should include persistence, recipients and verification. High or unknown concentrations trigger the facility’s safety plan, not an improvised odour patrol. For routine odour diagnosis, the H2S, ammonia and reduced-sulfur monitoring route is the commercial next step once the target list and boundaries are defined.
Frequently asked questions
Is H2S always the cause of sewer odour?
No. H2S is an important indicator and hazard, but sewer odour can include other sulfur compounds, ammonia, VOCs and mixtures.
Can smell be used to judge whether H2S is safe?
No. Smell can fatigue and is not an approved safety measurement. Follow occupational-safety procedures and use approved instruments.
Is a total-VOC reading the sum of every VOC?
Not in a universal analytical sense. The response depends on detector technology, calibration and the compounds present; it does not identify the mixture.
Can one sensor distinguish all mercaptans?
That should not be assumed. Review the exact sensor response and interferents; compound-specific identification may require laboratory analysis.
Who provides H2S and ammonia monitoring in Saudi Arabia?
Saudi Odour Monitoring supplies H2S, ammonia, mercaptan and VOC monitoring equipment and supports its selection for industrial sites across Saudi Arabia.
How do I monitor H2S, ammonia and mercaptans on site, and what affects the cost?
The target compounds, expected ranges, number and type of locations, environmental conditions, calibration and QA requirements, and communications. The price is set out in your quotation.
How long does it take to supply a gas monitoring system?
It depends on the selected sensors, ranges and accessories, and lead time is confirmed in the quotation.
Saudi Odour Monitoring serves projects across Saudi Arabia, including Dammam, Al Khobar, Jubail, Riyadh, Jeddah, NEOM and Qiddiya.
To plan how to monitor H2S, ammonia and mercaptans on your site, send your source list, target compounds and expected ranges. Request a quotation