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What are diesel engine exhaust emissions (DEEE)?

Diesel engine exhaust emissions, commonly abbreviated to DEEE or simply diesel fumes, are the complex mixture of gases, vapours, liquid aerosols and ultrafine particles produced when diesel fuel is burned in an internal combustion engine. The mixture contains nitrogen oxides (NO_x), carbon monoxide, carbon dioxide, sulphur dioxide, polycyclic aromatic hydrocarbons (PAHs), aldehydes and a high mass of soot — the elemental and organic carbon particulate fraction often used as the marker substance for occupational diesel exposure monitoring.

Diesel exhaust typically contains many times the soot mass found in petrol exhaust. Many of its components are individually hazardous, and the mixture as a whole has been classified as carcinogenic to humans (Group 1) by the International Agency for Research on Cancer. Diesel fumes are visible at much lower concentrations than petrol exhaust, but the most dangerous fraction — the ultrafine particulate — is invisible and easily inhaled deep into the lung.

Health effects of diesel fume exposure

Short-term exposure to diesel exhaust emissions causes irritation of the eyes, nose, throat and airways, headaches, light-headedness, nausea and an aggravation of existing asthma. These effects are usually reversible but signal that workplace exposure is poorly controlled.

Long-term, repeated exposure is the more serious concern. Sustained inhalation of diesel particulate has been linked to chronic bronchitis, reduced lung function and an increased risk of lung cancer; there is also growing evidence of an association with bladder cancer and cardiovascular disease. Because the disease latency can be decades, robust monitoring and recordkeeping today protects both the workforce and the employer’s long-term liability position.

Who is at risk?

Anyone working in, or close to, an enclosed or semi-enclosed space where diesel engines are running can be exposed. The risk is highest where engines idle for extended periods, where extraction is undersized or absent, and where natural ventilation is restricted. Sectors and roles we regularly assess include:

• Fire and rescue appliance bays
• Emergency generator and sprinkler plant rooms
• Rail depots, sidings and engineering shops
• HGV and bus depots, vehicle workshops
• Mining, quarrying and tunnelling operations
• Multi-storey and underground car parks
• Warehousing using diesel forklifts
• Construction sites with diesel plant in confined areas
• Marine engine rooms and dockside operations
• Agricultural buildings with running diesel machinery

How DEEE monitoring works

A defensible diesel exhaust assessment combines three things: a competent walk-through that maps where engines run, who is nearby, and for how long; quantitative air sampling that captures the actual exposure of named workers over a representative shift; and laboratory analysis that returns a reportable concentration in the units regulators recognise.

Personal sampling

A small, calibrated sampling pump is worn by the worker for a full shift, with a sampling head positioned in the breathing zone. This produces a personal eight-hour time-weighted average (8-hour TWA) — the metric most directly comparable to occupational exposure limits.

Static (area) sampling

Fixed sampling points are used to characterise specific zones — an appliance bay, a generator room, a loading dock — and to test the performance of local exhaust ventilation (LEV) and general dilution ventilation. Static data also helps identify peak emission events that personal sampling can mask.

Elemental carbon (EC) is the standard marker for diesel particulate matter and is measured to internationally validated methods such as NIOSH 5040. Real-time aerosol instruments are also used to map short-term concentration peaks during specific tasks, supporting targeted control measures.

Exposure limits and the legal framework

UK employers have a duty under the Control of Substances Hazardous to Health Regulations 2002 (COSHH) to assess and control exposure to substances hazardous to health, including diesel exhaust. The Health and Safety Executive (HSE) publishes Workplace Exposure Limits in document EH40/2005 (as amended), and many DEEE constituents — nitrogen dioxide and carbon monoxide among them — carry their own WELs.

Since 21 February 2023, diesel engine exhaust emissions have also been listed under the carcinogens and mutagens provisions of COSHH, with a binding occupational exposure limit value of 0.05 mg/m³ measured as elemental carbon (8-hour TWA), reflecting the EU Carcinogens and Mutagens Directive. Underground operations have a transitional limit and a longer compliance window. A documented DEEE assessment is the only practical way to demonstrate compliance with these obligations.

Practical controls — the hierarchy in real workplaces

Effective DEEE control follows the standard hierarchy of risk reduction. Eliminate the source where possible — for example by replacing diesel forklifts with electric equivalents, or by relocating idling away from occupied areas. Substitute lower-emission engines (Stage V, after-treatment fitted) where elimination is not feasible. Engineer controls through tailpipe extraction in fire stations and workshops, well-designed local exhaust ventilation in plant rooms, and adequate make-up air. Administrative controls — idling policies, scheduled testing windows, restricted access — reduce time-weighted exposure. Respiratory protective equipment is the last line of defence and must be face-fit tested.

Each of these controls only works if it is verified. Our reports include explicit, prioritised recommendations that name the control, the location, the responsible role and a sensible target date.

What our DEEE reports cover

Every Sysco Environmental DEEE report is signed off by a competent occupational hygienist and is structured to be useful to a site manager, an HSE inspector, an insurer and a board reader at the same time. It includes:

• A clear summary of the work carried out, sampling strategy and observations on existing controls and PPE.
• Tabulated sampling results with sample location, duration, method and analyst, benchmarked against WELs and the EH40/2005 limit for elemental carbon.
• An assessment of LEV and general ventilation performance, with proportionate improvement recommendations.
• A review of respiratory protective equipment selection, suitability and face-fit status (face-fit testing available as an add-on).
• Annotated photographs and schematics highlighting the issues found and the controls recommended.
• A prioritised action plan with named owners and target dates — not just a list of findings.
• Relevant HSE guidance citations applicable to your specific operations.