Ashtead Technology Ltd

Why instrument hire makes occupational safety sense

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Courtesy of Courtesy of Ashtead Technology Ltd


Decisions concerning the acquisition of occupational safety monitoring instrumentation are often made by operational staff that may not have visibility of the full financial implications of their choices. The following article will examine the factors affecting these decisions and explain why a strategic decision to hire instrumentation can deliver substantial and wide-ranging advantages.

The Management of Health and Safety at Work Regulations 1999 require employers and self-employed people ‘to carry out a suitable and sufficient assessment of the risks for all work activities for the purpose of deciding what measures are necessary for safety.’ However, the risks arising from toxic gases, dust, explosive mixtures and oxygen depletion can be complex and constantly changing. So, in addition to an initial risk assessment, ongoing monitoring is often necessary to ensure the protection of staff and others.

Employers may choose to conduct their own testing and monitoring, or they may prefer to employ the services of professional consultants to conduct the risk assessments. Either way, the employer of the consultant has to decide whether to purchase the instrumentation or to rent it.

The risks

Before examining the ways in which testing and monitoring should be undertaken, it is first necessary to consider the risks that need to be assessed.

Fire and/or an explosion can result from an excess of oxygen in the atmosphere, for example, from an oxygen cylinder leak, or an explosion may occur from the ignition of airborne flammable contaminants that may have arisen from a leak or spillage from nearby processes.
Toxic gases, fumes or vapours may also arise from leaks and spills, or from disturbed deposits or cleaning processes. Gases and fumes can accumulate in confined spaces such as sewers, manholes and contaminated ground. They can also build up in confined workspaces for welding, flame cutting, lead lining, brush and spray painting, or moulding using glass reinforced plastics, use of adhesives or solvents. Carbon monoxide, particulates and hydrocarbons may also become a problem in situations where the products of combustion are not exhausted adequately. Plant failure can also create gaseous hazards. For example, ammonia levels may increase if refrigeration plant fails or carbon dioxide may accumulate in some pub cellars following leaks from compressed gas cylinders.

Oxygen depletion in workplace air can cause headaches, breathlessness, confusion, fainting and even death. There are many situations in which this can occur; for example:

  • Workers breathing in confined spaces where replacement air is inadequate
  • Oxygen consumption by biological processes in sewers, storage tanks, storm water drains, wells etc.
  • Fermentation in agricultural silos or in brewing processes
  • Certain goods in cargo containers
  • Vessels that have been completely closed for a long time (particularly those constructed of steel) since the process of rust formation on the inside surface consumes oxygen
  • Increased levels of carbon dioxide from wet limestone chippings associated with drainage operations
  • Combustion operations and work such as welding and grinding
  • Displacement of air during pipe freezing, for example, with liquid nitrogen
  • Purging of a confined space with an inert gas to remove flammable or toxic gas, fume, vapour or aerosols

The COSHH definition of a substance hazardous to health includes dust of any kind when present at a concentration in air equal to or greater than 10 mg/m3 8-hour TWA of inhalable dust or 4 mg/m3 8-hour TWA of respirable dust. This means that any dust will be subject to COSHH if people are exposed above these levels. Some dusts have been assigned specific Workplace Exposure Limits (WELs) and exposure to these must comply with the appropriate limit.

Most industrial dusts contain particles with a wide range of size, mass and chemical composition. As a result, their effects on human health vary greatly. However, the Health & Safety Executive (HSE) distinguishes two size fractions for limit-setting purposes termed ‘inhalable’ and ‘respirable’.

Inhalable dust approximates to the fraction of airborne material that enters the nose and mouth during breathing and is therefore available for deposition in the respiratory tract. Respirable dust approximates to the fraction that penetrates to the gaseous exchange region of the lungs. Where dusts contain components that have their own assigned WEL, all the relevant limits should be complied with.

The financial justification for instrument hire

For most of us, when we need something, assuming funds are available, we buy it. At Ashtead Technology, we challenge that assumption; unless the required instrument is either very low cost or likely to be deployed on a frequent basis, it rarely makes sense to purchase the equipment. There are many reasons for this, but the most important is of course financial, however, operational staff are not always aware of the full cost of purchase, because the detail is hidden in the company's accounts.

Capital purchases are generally written off in the company accounts over a 3, 4 or 5 year period. This means that the cost of ownership is at least 20% of the capital cost per year and possibly over 33%. However, there are of course other costs of ownership - most instruments require regular maintenance and calibration which itself involves further costs both in terms of materials and labour. A gas analyser, for example, would require calibration gases and associated valves and safety equipment; trained staff would be required to ensure that the instrument is calibrated correctly, and consumables such as filters and replacement gases would be required. The same issues arise with other types of instrumentation; all of which require maintenance by suitably trained and qualified staff. Consequently, the annual cost of instrument ownership can easily exceed 50% of the purchase cost.

Another significant financial cost is the ‘opportunity cost’ of the money that is tied up in a purchase; capital expenditure on equipment represents money that could have been used for other purposes – for investing in raw materials, staff, training, marketing, new premises etc. Alternatively that money could have been invested and delivered a return.

In addition to the financial justification, there are many more reasons to hire...

Renting provides appropriate technology

Once an instrument is purchased, the company is committed to that technology for the next few years and this can be a major disadvantage. For example, if a company purchases a PID gas detector for the measurement of solvents, it may find later that there is also a requirement to monitor methane, and the PID would not be suitable for this, so a second analyser would be necessary; an FID for example. Similarly, the company may discover at a later date that solvent speciation is necessary, which again, the PID would fail to achieve.

The same principle applies to other applications. For example, if a basic infrared camera is purchased and it later transpires that higher resolution images are required, a second more expensive camera would be necessary.

From a corporate perspective, instrument purchase can have negative implications because instruments are often shared amongst different departments and between different sites. However, it is unlikely that one technology or one particular instrument is able to meet everybody's needs, so it is likely that each person will seek to acquire their own instrument; firstly to ensure that they get the kit that they need, but also so that their access to instrumentation is not limited because it is in use elsewhere. If each person is allowed to purchase their own kit; whilst this might be an extremely costly option, it does at least encourage ‘ownership’ so that the equipment is properly maintained. In contrast, shared ownership often results in poor maintenance because none of the staff take responsibility for ensuring that the equipment is serviced and maintained correctly.

Renting instrumentation ensures that all staff have continual access to a range of different technologies, so they do not have to 'make do' with whatever happens to be available at the time they need it. If a company has purchased an instrument, its staff are more likely to use it 'because it is there' rather than because it is the most appropriate technology.

Renting provides access to new technology

One of the problems with buying an instrument is that your technology is then stuck in a moment of time; inevitably new instruments are developed that are better than their predecessors, but once an instrument has been purchased it is not possible to take advantage of new technology. In contrast, with the benefits of scale, Ashtead is able to continually invest in new technology so that the rental fleet provides access to the latest technology and customers are therefore able to choose the instruments that best meet their needs.

Renting eliminates storage and maintenance costs

One of the common features of all instruments is that they require regular maintenance and in many cases calibration. This is often a skilled activity that requires training and appropriate equipment. Ashtead Technology's engineers are therefore equipped with all of the necessary equipment to service and maintain every instrument in the rental fleet. They are also trained by manufacturers, so that all instruments can be delivered tested and ready for immediate use. Storage can also represent a cost for the larger pieces of equipment, especially if it is not possible to store the instruments in the same location as the main users.

Technical support from rental companies

Instrumentation is constantly evolving; newer instruments are usually more accurate, more sensitive, faster, lighter, and easier to use. However, the array of instruments available can be bewildering so it is often helpful to discuss options with an Ashtead Technology engineer before making a choice, and then after the instrument is delivered, many customers value telephone support during the setup and operation of the instrument.


The basic premise behind Ashtead Technology’s business is an intense focus on providing customers with exactly the right equipment at the precise moment that they need it. We therefore seek to become our clients’ instrumentation partner; saving them time and money, and ensuring that they always have access to the best available technologies. This is achieved by:

  • Continually searching the market, looking for the best technologies from the world’s leading suppliers
  • Utilising expert knowledge and buying power to ensure that our fleet of instruments includes a broad selection of the best available technologies
  • Manufacturer training for our engineers
  • Investing in the equipment, spares and consumables for servicing, calibrating and maintaining the entire instrumentation fleet
  • We invest in these measures so that our clients don’t have to.

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