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Selected ion flow tube mass spectrometry (SIFT-MS) has been used to analyse on-line and in real time the exhaust gas emissions from a Caterpillar 3304 diesel engine under different conditions of load (idle and 50% of rated load) and speed (910, 1500 and 2200 rpm) using three types of fuel: an ultra-low-sulphur diesel, a rapeseed methyl ester and gas oil. SIFT-MS analyses of the alkanes, alkenes and aromatic hydrocarbons in the headspace of these fuels were also performed, but the headspace of the rapeseed methyl ester consists mainly of methanol and a compound with the molecular formula C4H8O. The exhaust gases were analysed for NO and NO2 using O2+* reagent ions and for HNO2 using H3O+ reagent ions. The following aldehydes and ketones in the exhaust gases were quantified by using the combination of H3O+ and NO+ reagent ions: formaldehyde, acetaldehyde, propenal, propanal, acetone, butanal, pentanal, butanone and pentanone. Formaldehyde, acetaldehyde and pentenal, all known respiratory irritants associated with sensitisation to asthma of workers exposed to diesel exhaust, are variously present within the range 100-2000 ppb. Hydrocarbons in the exhaust gases accessible to SIFT-MS analyses were also quantified as total concentrations of the various isomers of C3H4, C3H6, C4H6, C5H8, C5H10, C6H8, C6H10, C7H14, C6H6, C7H8, C8H10 and C9H12.

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Airflow visualization in the workplace to assess containment, ventilation, or general air movements is often carried out using smoke tracers. The most prevalent method uses a disposable smoke tube that generates a plume of concentrated sulfuric acid fume. However, use of the smoke tube exposes occupational hygienists to the risk of sulfuric acid exposure through inhalation or dermal contact, as well as injury from sharps. Following concern over the potential health hazard associated with smoke tube usage, alternative flow visualization methods and technologies have been reviewed. Methods of generating smoke or bubbles other than using smoke tubes suitable for visualizing air movements include heated element smoke generators, combustion generators, generation of metallic chlorides and ammonium chloride, generation of neutral density bubbles, and water fog generation. Some of these methods are applicable in specific workplace situations. However, there is no commercially available smoke or bubble generator currently available that matches the smoke tube for cost effectiveness, ease of use, and wide applicability, while also reducing the potential health risks associated with smoke tube usage. Despite this, certain technologies, in particular water/glycerol smoke generation using heated element generators, have the potential to be developed into viable alternatives to the smoke tube. Thus, with further development, an air movement visualization method that poses a significantly lower health hazard than the smoke tube is feasible.

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