Nitrous Oxide’s Role in Drug Driving Offences

Nitrous Oxide’s Role in Drug Driving Offences

Written by: Christopher Smith, PNLD's Traffic Law Consultant

Not reviewed after the date of publication - 25 August 2025

This article has been written by PNLD’s traffic law consultant, Christopher Smith, in conjunction with information supplied by Francis Meylan the Chair of the National MG DD Form Editing Group and Drink Drug Drive Liaison Officer and PC John Lansley (Impaired Driving Specialist). It covers the main issues to be aware of when dealing with drivers who have taken nitrous oxide.

Nitrous Oxide

Nitrous oxide, also known as ‘NOS’ or ‘laughing gas’, is a colourless sweet-tasting gas that was discovered by the chemist Joseph Priestly in 1772.

It has a wide variety of uses, for example:

• as an anaesthetic and analgesic in medicine/dentistry,
• propellant in the catering industry,
• food additive,
• component in vehicle fuel, and
• model rocketry.

It’s usually sold in small silver cannisters or larger cylinders but is often abused by being inhaled from a balloon – discarded cannisters and ballons can be seen in lay-bys and on roadside verges.

From 8 November 2023, nitrous oxide has been a Class C drug under the Misuse of Drugs Act 1971.



Whilst it is not an offence to import nitrous oxide, possess, supply or manufacture it for lawful purposes, it is an offence to import, supply or possess it for wrongful inhalation – contrary to section 5(2) of, and Schedule 4 to the Misuse of Drugs Act 1971 (MDA 1971). This is an either way offence with a maximum penalty of:

Summary: 3 months or £1,000, or both.
Indictment: 2 years or a fine, or both.

Professor Philip John Cowen, Professor of Psychopharmacology at Oxford University produced a Report in the form of a witness statement for the Home Office in 2016 regarding nitrous oxide, he said:

‘Nitrous oxide continues to have medical use as a component of general anaesthesia as well as in other clinical procedures and situations where sedation and analgesia are useful. It is also being explored as a possible therapy for treatment resistant depression.

It has been known for over 200 years that nitrous oxide has psychoactive effects in addition to its anaesthetic and analgesic properties.

Generally, the effect is to elevate mood and produce changes in subjective mental state that are typically associated with psychedelic agents. These changes take the form of alterations in body image, sensation and perception.

This is consistent with the observation that many of the effects of nitrous oxide are similar to another well-known NMDA receptor antagonist, ketamine.’

The effects of inhaling nitrous oxide are noted as:

• Single inhalation – will result in effects starting almost immediately, peaking about 10-30 seconds after inhalation and then rapidly diminishing. It produces a euphoric, pleasant, joyful, empathogenic (generating a state of empathy) and sometimes hallucinogenic effect, and causes a deep ‘silly’ voice.
• If the dose is repeated – effects reach a plateau about 30-60 seconds after the first breath.

Whilst the user often feels back to ‘normal’ within about 1-5 minutes after the last inhalation, some users report that effects such as a sense of well-being can be felt for up to 30 minutes after last use.


 

Short term temporary side effects include pins and needles, numbness, dizziness, dissociation, disorientation, loss of balance, impaired memory and cognition and weakness in the legs.

The Drug Influence manual (Impairment Testing and Drug Recognition) shows the following symptoms that would be associated with nitrous oxide:

‘Dizzy / light headed – Nausea – Bloodshot Eyes – Distorted time and distance perception – flushed/sweaty appearance – intense headache – non-communicative – slow, slurred speech, confusion, lack of muscle control.’

Driving whilst affected by nitrous oxide

 

Cases involving drivers under the influence of nitrous oxide are investigated using the provisions of section 4 of the Road Traffic Act 1988 (RTA 1988). For this offence impairment must be proved and this is defined in section 4(5), it states:

‘For the purpose of this section, a person shall be taken to be unfit to drive if his ability to drive properly is for the time being impaired.’

In Bradford v Wilson (1984) [PNLD ref: C100432], it was held that a substance taken in the body which was not a drink and not taken as food but which affected the control of the body was capable of being a drug. Accordingly, B’s action in sniffing glue and taking by inhalation the constituent chemicals of the glue (Toluene) was correctly convicted under what is now section 4 of the RTA 1988.

Practical issues for the police in prosecuting a section 4 unfit through nitrous oxide offence are:

• proving impairment, and
• proving the presence of a drug.

Although having an evidential specimen is not a prerequisite for a section 4 offence, the impairment must be linked to being caused through drink or drugs.

In most drug drive cases, it is the norm to have an evidential specimen to prove the presence of a drug or drugs. However, nitrous oxide is almost impossible to detect in the blood and has a very rapid half-life. One of the current Forensic Service Providers stated in 2020 the following:

‘It is in theory possible to test for nitrous oxide in blood, but it is not something we do.

However, unless a blood sample is collected very quickly after suspected use/exposure the chances of detection are unlikely.

The half-life of nitrous oxide is very rapid (only approximately 5 minutes) so within 5 minutes the concentration would be half, within 10 minute a quarter and so on.

Also due to the volatility of nitrous oxide it may not be very stable in collected samples.

Unfortunately, I am unable to find anywhere that would conduct this analysis.’

Therefore, a section 4 unfit through drugs prosecution on the basis the driver was impaired will not have a blood specimen which on analysis was positive for nitrous oxide.  The evidence to prove impairment, and that it was through drugs (nitrous oxide), will be all based upon what was witnessed.

Investigating suspected Unfitness through nitrous oxide inhalation

 

Very prompt and detailed evidence gathering will be the key to dealing with cases involving the use of nitrous oxide. The following list covers the main points:

• Evidence of poor driving.
• Body worn camera evidence of the first interaction with the subject.
• Have they been seen inhaling?
• Seize paraphernalia to prove nitrous oxide was in their possession. Common items are NOS Crackers (Administration tool), latex balloons, small NOS canisters (usually silver or gold).

• If there is an officer preliminary impairment test trained and authorised, administer the test ASAP.
• Evidence if the subject’s demeanour changes rapidly. This is consistent with having inhaled nitrous oxide and is key – this is known as the ‘cyclic action’ of nitrous oxide.
• It’s known that drivers video themselves or video is taken on phones by other vehicle occupants – can this evidence be obtained?
• If impairment was witnessed by officers/public, obtain this evidence and consider arrest using section 24 of PACE [PNLD ref: D227] for a section 4 unfit offence. And if applicable the Misuse of Drugs Act 1971 [PNLD ref: S68] possession offences.
• Consider a preliminary drug test if grounds for requiring co-operation apply (suspect drug in the body, moving traffic offence, road traffic collision).
• On arrival in custody (if no positive preliminary drugs test has been carried out), using MGDD/A and B forms, put the suspect before a HCP/Dr for them to state –‘condition might be due to some drug’ under s.7(3) of the RTA 1988 [PNLD ref: D973] using the of case of Angel v CC South Yorkshire Police (2010) EWHC 883 (Admin) [PNLD ref: C3208], on the basis there is evidence they were impaired at time of driving through a suspected drug. The High Court’s decision in the Angel case is relevant here because the issue the court was dealing with was whether the words in s.7(3)(c) i.e.

CPS now provide the following advice in relation to this – see ‘Doctor's advice to Constable re influence of drugs under section 7(3)(c) RTA 1988’:

‘Under section 7(3)(c) RTA 1988 a constable may require a driver to provide a laboratory specimen when a medical practitioner has advised them that the condition of the driver might be due to a drug. The purpose of this provision is neither to prove that the driver is, or that the doctor believes him to be, under the influence of drugs - but simply to advise that the driver's condition might be due to some drug. The doctor is not prohibited by the words of that statute from taking into account any fact or matter which they feel to be relevant. They are not restricted to considering the condition of the driver at the time of the examination. Officers are now frequently testing for driver impairment due to drugs at the roadside. The tests are primarily based on the physical response of the driver to certain tasks. The doctor may consider the results of such tests when they advise a constable under section 7(3)(c) RTA 1988.’

• If the Dr/HCP will say ‘that the condition of the person required to provide the specimen might be due to some drug’ obtain a blood specimen preferably, although it could be urine, as it’s a section 4 offence.
• Although at present nitrous oxide cannot be detected in the blood, it is understood that CPS are content it is legitimate to use the power to require an evidential specimen and to have it analysed for drugs.
• If a specimen is obtained, other drugs may be detected for a section 5A [PNLD ref: D2902] or section 4 offence.
• If no drugs are detected, this supports the argument the impairment witnessed was consistent with nitrous oxide.
• Interview the subject in accordance with PACE regarding all the evidence.

Offences

Depending on the circumstances, the following offences could be considered – the list isn’t exhaustive:

• Driving whilst unfit through drugs – section 4 of the RTA 1988 [PNLD ref: D2902],
• Dangerous Driving – section 2 of the RTA 1988 [PNLD ref: D698]
• Driving without Due Care and Attention – section 3 of the RTA 1988 [PNLD ref: D699]
• Driver of a motor vehicle not being in a position to have proper control of the vehicle or a full view of the road and traffic ahead – regulation 104 of the Road Vehicles (Construction and Use) Regulations 1986 [PNLD ref: D2687]
• Possessing nitrous oxide for wrongful inhalation – section 5 of the MDA 1971 [PNLD ref: D2104]. Ask the prosecutor to suggest to the court they disqualify the driver using section 163 of the Sentencing Act 2020 (driving disqualification - availability for any offence ) [PNLD ref: D45216].

Conclusion

As can be seen from the above, in reality, it is very difficult to prove to a level to satisfy a court that a driver was unfit through nitrous oxide because it’s almost impossible to detect in the blood and has a very rapid half-life. However, we understand a conviction at magistrate’s court has been successful as a result of the police stopping the driver as he was actually inhaling NOS and he had all the paraphernalia with him.

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