All you need to know about a Safety Critical Worker Medical

Posted By Stephanie Hancox on 2017-12-18 13:08

We provide Safety Critical Worker Medicals across the United Kingdom. If you require a fit for work medical, give us a call on 01455 234 600 or contact us online now.


So you've had a look   into what occupational health surveillance you require and one of them is a Safety-Critical Worker Medical which you may know involves:

• A baseline Safety Critical Worker health questionnaire to establish any current or previous medical/psychological health history (we send this to you at the company for the employees to complete ready for when we arrive on site)

• Blood pressure measurement

• Height, Weight & Body Mass

• Audiometry (Hearing test)

• Spirometry (Lung function test)

• Vision

• HAVs

• Urinalysis for diabetes or other health issues

• Musculoskeletal assessment 

• Drug & Alcohol testing 

However, do you know how these are assessed and if so are you confident in informing your employees what is involved in each assessment/surveillance?

What's involved in a Safety Critical Medical?

A Safety Critical medical starts off with a standard employee questionnaire which briefly looks into possible hazards and/or risks to an individuals health for example if they are exposed to certain chemicals and/or substances which could cause dermatitis etc along with a quick look at previous employment. This is a self-asses questionnaire which the employee must fill out and have ready to hand into the relevant OH Professional at the time of their screening. The OH Professional will be able to use the questionnaire to identify any areas which may be of concern.

Blood Pressure Measurement -  If you've ever visited a GP and had your Blood Pressure checked, you will be familiar with the process. The process is pretty straightforward and pain-free. The OH Professional will wrap a cuff around the individual's arm which will have a gauge on it to measure the blood pressure. Once the cuff is inflated, the OH Professional will start deflating the cuff and take note of the readings on the gauge.                                                                The blood pressure is measured in 2 parts. The first being the Systolic blood pressure which is the pressure within the blood vessels whilst the heart beats, the second measurement is the diastolic blood pressure which measures the pressure in the blood vessels again but when the heart is at rest. 

When written the measurements will be written as Systolic over Diastolic measurement. An example of a healthy blood pressure would be 120/80 however as seen below you can see how these measurements are used to determine the category of your blood pressure. 

Height, weight and Body Mass - It's an important aspect of health surveillance to ensure that an employee is able to complete tasks which put any pressure on their health, this is why during ana SCWM an OH Professional will note your height and weight to calculate your BMI and be able to advise on where improvements could be made to ensure your employees are doing what they can to stay healthy. Again, just like the Blood pressure surveillance, this surveillance is relatively straightforward, your height will be accurately measured and your weight will be noted based on the result that the scales give. 

Audiometry - If we attend with our vehicle, our OH Professional will explain to the employee how the audiometry assessment is done and how their hearing is tested before being asked to sit in the booth, however, if we don't attend site with our trailer and the surveillance is carried out in a meeting room, for example, the same procedure takes place however minus the booth. 

The employee being tested will wear a pair of our top of the range headphones and be given a trigger to press when they believe they can hear a certain tone/noise. Starting with the right ear, our OH Professional will test in the following tones measured in Hz's. 

1000Hz    2000Hz    3000Hz   4000Hz   6000Hz   8000Hz   then 250Hz and 500Hz

The results from these frequencies excluding the 250Hz and 500Hz and 8000Hz are taken into account to determine what category of hearing the employee is classed as. Although they aren't taken into account for a final result, the 250Hz and 500Hz frequencies are tested as a standard procedure to ensure the employee can hear low frequencies okay. To ensure there are no false positives from the surveillance, the timing between the frequencies are to be unpredictable.

Spirometry - Spirometry Tests (Lung Function Tests) aims to detect early damage to lung function from exposure to respiratory sensitizers and other substances that have the potential to cause serious ill health. The tests we undertake provide employers with a baseline for future reference and they can also assess employees’ fitness to work. Lung function testing should be performed on all employees potentially exposed to irritant dusts, gases and vapours in the workplace. The surveillance measures the volume of air that an individual can exhale in one forced breath along with the amount of air that can be exhaled in one second. 

During a Spirometry surveillance, the employee will be asked to blow into a spirometer a maximum of 8 times to ensure 3 good results are gathered. These results are then reviewed and compared to the "normal" results of a healthy person in your demographic group (sex, age, height). If the results come up abnormal, it is usually clear if the problem is obstructive or restrictive. Although a spirometry surveillance is straightforward, it is common to feel lightheaded and dizzy afterwards. 

Vision - At Healthscreen, we use an automated Keystone machine to test an employee eyesight and usually takes around 10 minutes to complete. However, some providers may still use the Stellen Scale. You will be asked to sit in front of the Keystone machine and adjust the chair height and/or angle of the viewer accordingly. There is a sensor within the viewer which can detect when the face is properly positioned, however, this can be manually over-ridden if the OH Professional believes the individual is in the correct position. 

If eyesight has been corrected, glasses or contacts should only be worn on the first stage of the test, and reading glasses only on the VDU and near vision test. 

After the test, the OH Professional will review the results received and advice accordingly.

HAVS - During an initial Safety Critical Worker Medical, an employee will be asked to fill out a self-assessed Tier 1 questionnaire which is then reviewed by an OH Nurse to determine whether the answers given requires a referral to HAVS Tier 3. SCWM's which are done the following years then requires an employee to fill out another self-assessed Tier 2 questionnaire, again these answers are reviewed and if applicable a referral to HAVS Tier 3 is made. 

Click here for more information on the HAVS Tiers and how each of them is assessed.

Urinalysis for diabetes or other health issues - During a surveillance for diabetes and/or other health issues, an individual will be given a plastic cup labelled with their name and personal details i.e. date of birth. The individual will then collect a sample of urine in a clean private bathroom. We recommend the "mid-stream" of urine to be collected to avoid contamination of bacteria or cells, this is also known as the "clean-catch". 

A test strip is then placed within urine sample which will detect the presence of glucose and/or ketones. Ketones are most commonly found in people who have type 1 diabetes and if these are allowed to build up to high levels a condition known as Ketoacidosis can occur. Furthermore; Urine testing doesn't test your current levels of glucose but rather any glucose that has managed to enter the urine. 

If the presence of either of these is noted, we recommend a visit to the GP to have a blood glucose test. A doctor will also be able to provide more insights into the causes and medications which should be used if required. 

 Musculoskeletal assessments - On average the Musculoskeletal surveillance takes around 10 minutes, and is again fairly straightforward. Prior to the surveillance a self-assess questionnaire would have been filled out and is used to identify and pre-existing MSD (Musculoskeletal Disorders) along with and pain or discomfort, Any previous treatment for MSD and whether your current job role can have an impact on your ability to perform a job role safely. The OH Professional will assess an employees arms, legs, and spine. 


As shown in the diagrams, certain aspects are looked at and noted for any abnormalities. For example:

  •   - The person's gait (manner of walking), this is observed by asking the employee to walk a number of steps before turning around and walking back. 
  • - Observations are made of the factors noted in the diagrams. 

- During the observations, an employee will be asked to stand in a range of positions with hands either at the side or behind the head or hands placed on the table depending on what aspect is being observed. And at times, the employee may be asked to sit or lie down on a coach. 










Drug and Alcohol Testing - Drug and Alcohol tests can usually take around 10 minutes. The following is for the current drug tests being used however different drug tests may work differently.

Firstly the employee being tested is asked to place a swab into their mouths behind their teeth, this will collect Salvia and once enough has been collected (the stem of the collector will change colour once enough has been collected); the collecting swab is screwed into the accompanying tube. The design of the accompanying tube means the salvia can be "strained out and delivered equally to each individual test stripe due to the concave base. Results are usually available within 10 minutes, 1 line will indicate a positive result to the particular substance whereas 2 lines will indicate a negative result. If the result comes back positive, a second sample is taken and sent to a laboratory for further testing and confirmation on the abused substance. 

The Alcohol testing is completed via the use of a breathalyzer (breath alcohol testing device), As alcohol isn't instant;y digested when consumed but rather absorbed into the bloodstream; Once the blood passes the lungs, a percentage of the alcohol in the bloodstream can be transferred through the membranes of the alveoli. Once in the alveoli, the alcohol evaporates into the alveolar air, which is measured by the breathalyzer when the individual breaths into it. It is thought that the ratio of alcohol in the alveolar air to the blood in 2,100ml:1ml. 

If alcohol is present, a reading will be given on the breathalyzer. If alcohol is present, no further surveillance or testing is required, and the employee will be subject to the procedure presently enforced in the workplace in regards to alcohol. 

Safety Critical Worker Medicals should only take around an hour to complete per employee, however, may differ depending on how long each individual surveillance may take. Once all the results have been collected and reviewed by our OH Nurse, a comprehensive report is written up and certificates are produced for the employees who have passed. 

For more information on either the Safety Critical Worker Medical or other services we have to offer, please don't hesitate to get in touch. 



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