Industrial Disease Risk Among Hospital Staff Working with Deprox Machines?

An investigation, conducted by the Telegraph, has unearthed that potentially thousands of NHS staff are at risk of inhaling toxic vapour from Deprox cleaning machines. It has been alleged that short-term exposure onsets a host of symptoms, such as:

  • Nose bleeds;
  • Coughing;
  • Vocal changes;
  • Breathlessness;
  • Itching, burning and watering of the eyes; and
  • Chest infections.[1]

What Are Deprox Machines?

Deprox, manufactured by Hygiene Solutions, is a regulated vaporisation system for bio-decontaminating enclosed spaces.[2] It is the size of a small fridge and is ideal for use in healthcare settings, particularly after infected patients have been discharged.

In hospitals, the machine is typically wheeled into an empty ward, which is then sealed so that no air can escape. When the machine is turned on, it pumps out hydrogen peroxide vapour (visually resembling a ‘mist’ or ‘fog’), which disinfects all surfaces that it comes into contact with, even killing methicillin-resistant Staphylococcus aureus (MRSA).[3] The decontamination cycle lasts approximately 2-hours, though affected areas must remain out of action for 4-hours.[4]

The benefits of Deprox fumigation include a reduced risk of environmental contamination and patient infection, cost savings, extended bed occupancy and a one-size fits all method that alleviates uncertainty.

For example, in November 2012, Deprox machines were used to contain a norovirus at a Worcestershire Acute Hospitals NHS Trust-run hospital.[5] This took just 5-days, as opposed to 2-weeks, had the system not been used. At the time, Stewart Messer, Chief Operating Officer of the affected NHS Trust, praised the innovative cleaning method:

‘The system is almost 100 per cent fail-safe and this is a good example of the trust adopting the latest technology’.

How Prevalent Are Deprox Machines?

Responses to Freedom of Information (FOI) requests, submitted by The Telegraph, have identified that Deprox machines were first introduced in the NHS in 2012 and are currently being used at over 100 hospitals across England and Wales, at a cost of at least £2.1 million. ‘At least’, because many NHS Trusts refused to disclose ‘commercially sensitive’ information. 

Are Deprox Machines Safe?

A spokesperson for Hygiene Solutions stated that, when ‘used correctly’, its ‘ground breaking technology’ has been proven to be both ‘safe and effective’.

What is more, Hygiene Solutions pledges to offer operator training, support and advice as part of its commitment to hospitals and their staff. However, a company spokesperson warned that:

‘As with all similar products, the operator instructions and the equipment carry warnings about their safe use and it is important that the operator must perform the required steps correctly when using the equipment’.

In spite of this, the Health and Safety Executive (HSE), having concluded a 4-year investigation into the Deprox decontamination process in July 2019, believes that Hygiene Solutions should be doing more to protect Deprox users, e.g. providing hydrogen peroxide monitoring equipment.

Industrial Disease Claims Involving Deprox-Released Hydrogen Peroxide?

As stated above, at least 100 hospitals across England and Wales use Deprox machines. Consequently, there is potential for substantial numbers of employers’ liability claims to be brought by staff who operated (or were in the vicinity of) Deprox machines, without adequate training or protective equipment, and suffered personal injury.

As such, hypothetical claimants would likely assert breaches of the Control of Substances Hazardous to Health Regulations (as amended) 2002 (COSHH).

The short- (15-minute) and long-term (8 hour) workplace exposure limits (WEL) for hydrogen peroxide vapour are 2 parts per million (ppm) and 1 ppm, respectively.[6]

Deprox systems contain 5% hydrogen peroxide, which is 6-times less than the competitor Bioquell Q10 system. Nevertheless, peak aerial hydrogen peroxide values have been recorded at 29 to 46 ppm during Deprox cycles. The same set of records also documented a mean value of 3.3 ppm at the end of a Deprox cycle, i.e. above the WEL.[7]

Moreover, silver nitrate has been detected on Deprox decontaminated surfaces at 1.5 to 2.5 mg/m2, but not on Bioquell Q10 decontaminated surfaces.

Silver nitrate, like hydrogen peroxide, is also an irritant and is yet to be approved for use in biocidal preparations in the UK – see Article 17 of EU Regulation No 528/2012. The significance of making silver nitrate-containing biocidal products available on the market was confirmed by HSE’s Chemicals Regulation Division, in November 2016:

‘It would currently be illegal to make available and use a PT2 biocidal product, containing silver nitrate as the active substance, as silver nitrate has not yet been approved as a PT2 active substance and is being assessed as a new active substance’.

Settlements Agreed in Wales

This year, NHS Trust employer, the Abertawe Bro Morgannwg University (ABMU) health board, settled 2 claims, advanced by domestic managers, for a 5-figure sum.[8]

The Welsh health board purchased 9 Deprox machines in 2014 and 2015, but in October 2016, the devolved national Government was informed that the cleaning procedure had been ‘suspended on all ABMU sites’, after concerns were raised over ‘high concentrations’ of exposure to ‘harmful chemicals’, with domestic staff having complained of ‘skin irritation, nose bleeds and coughing’.[9]

AMBU’s Assistant Director of Nursing, Infection Prevention and Control, Lisa Hinton, caveated that only a ‘small’ proportion of hospital staff presented with symptoms, though an alternative means of decontamination replaced Deprox without reintroduction.[10]

Industrial disease solicitors, acting for the since-compensated ABMU health board workers, argued that it had breached its duty of care as an employer by failing to provide protective gear for machine operators and failing to provide gas monitors to measure chemical concentrations against recommended exposure limits when re-entering decontaminated areas.

Coincidentally, both claimants reported having suffered unexpected persistent epistaxis (nosebleed), which became a regular occurrence in the months that followed. As such, neither claimant immediately made the connection between Deprox and their deteriorating physical health.

One of the claimants, 51-year-old, Derek Baines, supervised up to 90 staff members during his shifts. The other claimant (nameless for anonymity purposes), explained that when Deprox was initially rolled-out and traditional cleaning methods ceased, she was told:

‘… it’s fine, it’s safe, go in, hold your breath and open the windows’.

As time passed, Mr. Baines noticed that his nosebleeds stopped and his fatigue improved.

However, the long-term impact of inhaled Deprox fumes on employee health is unknown.

That being said, hydrogen peroxide is not classifiable as to its carcinogenicity to humans and, on the basis that hydrogen peroxide is rapidly decomposed by the body, chronic toxicity is unlikely, with the exception of chronic irritation of the respiratory tract, partial or complete lung collapse and beaching of the skin and hair.[11]


[1] Camilla Turner, ‘NHS staff at risk of inhaling toxic fumes from cleaning machines, investigation finds’ (27 July 2019 The Telegraph) <> accessed 29 July 2019.

[2] ‘Deprox’ (Hygiene Solutions) <> accessed 2 August 2019.

[3] Eleni Mavrogiorgou et al., Evaluation of cleaning effectiveness in a tertiary hospital following hydrogen peroxide (HPV) fumigation using surface contact plates and adenosine triphosphate (ATP). Healthcare Infection, 2013, 18,45–46. <> accessed 2 August 2019.

[4] ‘Decontamination device kills hospital germs’ (20 December 2012 European Cleaning Journal) <> accessed 2 August 2019.

[5] ‘HPV fogger used to clear wards at Redditch hospital of norovirus’ (14 November 2012 Building Better Healthcare) <> accessed 2 August 2019.

[6] EH40/2005 Workplace exposure limits’ (2018 HSE) <> accessed 2 August 2019.

[7] Clinical Microbiology and Virology, University College London Hospitals NHS Foundation Trust, London, UK, ‘Response to letter of Singh K “Role of silver nitrate in the efficacy of hydrogen peroxide aerial decontamination systems” regarding S Ali et al. “Efficacy of two hydrogen peroxide vapour aerial decontamination systems for enhanced disinfection of methicillin-resistant Staphylococcus aureus, Klebsiella pneumoniae and Clostridium difficile in single isolation rooms”’ <> accessed 2 August 2019.

[8] Oakwood Solicitors have advertised hydrogen peroxide vapour claims as being worth up to £10,000. <> accessed 2 August 2019.

[9] <> accessed 2 August 2019.

[10] The Government memo stated that in tests, directed by ABMU health board Officials, 10 out of 20 employees reported coughing and itching, burning and watering of eyes, while 8 out of 20 employees (40%) reported breathlessness.

[11] ‘Toxic Substances Portal - Hydrogen Peroxide’ (ATSDR) <> accessed 2 August 2019.