As firefighters, we should constantly seek to update our knowledge and awareness of health, safety and performance issues. One topic that has attracted media attention lately is that of the dangers of drinking too much water, especially in light of people being encouraged to drink plenty to maintain hydration levels.

Since hydration is of particular importance to operational personnel, the following information should be considered.

Current drinking guidelines

The general guidance we currently provide regarding volumes, was originally developed for wearing BA in the fire training unit, hence the references to working in hot environments and performance in the heat. Obviously the guidance is relevant to working in hot operational environments or at high rates of extended periods (e.g. Grass Fires), but it is difficult to know when this is going to happen, unlike in training.

So while it is important to be well hydrated on station, in preparation for calls, the guidance is aimed at extended physical work and / or work in heat and would probably be excessive all day with such exertion.

Why must drinking guidelines be general?

The problem with providing drinking guidelines is that they must be general, as people sweat at different rates for the same tasks, will carry out different tasks on the fire ground, produce different amounts of salt in their sweat, have different body sizes (therefore fluid volume), begin a shift at different states of hydration and therefore will need to drink different amounts to keep well-hydrated.

Why is drinking too much water a problem?

Over drinking (hyponatremia: hypo – denoting a deficiency or abnormally low level, natremia – pertaining to sodium) it is quite unusual, but can happen, and has recently been an issue for marathon runners.

When a person is sweating profusely for extended periods of time, drinking too much water becomes a problem because the body is losing water and salt in the sweat, but only the water is being replaced. This dilutes the electrolyte (salt) content of the plasma (the liquid part of the blood), and the imbalance, or lack of salt, can interfere with brain, heart and muscle function.

In extreme circumstances, this can lead to things such as swelling of the brain and water in the lungs, which may result in death. However, in less extreme circumstances, the effects are less severe.

Guidance on avoiding over-drinking

When exercising for less than an hour, water will be adequate because the salt in our food should replace that lost in sweat (assuming you eat a regular, balanced diet).

If exercising and sweating profusely for more than an hour, 150-200 mls of fluid every 20 minutes is wise. The fluid should contain some salt to replace that lost as sweat (e.g. a sports drink), or the person could eat salty snacks (but this is not practical on the fire ground unless resting and in a hygienic environment). This will help prevent both dehydration and hyponatremia. Also, a sports drink contains carbohydrate, which provides energy and helps to absorb water salt.

You should not drink any more than 1 litre per hour – this is heading towards excessive fluid intake.

The signs and symptoms of heat exhaustion and heat stroke are similar to that of hyponatremia, and can be confused. The symptoms of heat exhaustion include dizziness, headaches, nausea, fatigue and muscle cramps. Heat stroke includes the above symptoms, but will be accompanied by mental status changes, such as who they are, where they are, and what day it is. Somebody suffering from heat stroke will also have an excessive body temperature. With hyponatremia, people also feel very ill and experience mental status changes, but do not have the same high body temperature as with heat stroke. They also vomit forcefully and repeatedly and, unlike those with heat exhaustion, do not feel better by resting or cooling off. It is therefore important to be prepared and be aware of the physiological situation of yourself and others.

If you notice any of the above symptoms in yourself, or someone you are training or working with, stop what you are doing immediately and get into the shade. A good idea is to fill a bucket with cold water and submerge the hands of the affected person up to just over the wrists in it. Then seek immediate medical attention.

Additionally, dehydration is extremely important to firefighters, whether they are maintaining fitness levels or going about their normal day-to-day work.

Firefighters are regularly subject to intense heat and physical exertion, which will produce excessive sweating, not just from fighting fires, but also from other incidents. Unlike when training, water intake when working is not as easy to maintain and the risk of becoming dehydrated increases.

Dehydration means that your body does not have as much water and fluids as it should which leads to major problems if it goes unchecked. When the body loses fluids through sweating, or diarrhoea if you are ill, it also loses salts, called electrolytes, which keep the body functioning properly. The risk also increases in hotter temperatures where the rate of sweating increases. These fluids need to be replaced to keep the body hydrated.

Dehydration can be classed as mild, moderate or severe based on the percentage of body weight lost in water. When severe, dehydration is a life-threatening emergency.

Causes, Incidents and Risk Factors

Your body may lose too many fluids from the following:

  • Vomiting and Diarrhoea
  • Excessive urine output, such as with uncontrolled Diabetes or Diuretic use
  • Excessive sweating (e.g. Firefighting or Exercise)
  • Fever.

You might not drink enough fluids because of:

  • Nausea
  • Loss of appetite due to illness
  • Sore throat or mouth sores
  • You are too busy!


It may only take a 2% reduction in water within the body for the following symptoms to appear:

  • Dry or sticky mouth
  • Low or no urine output; concentrated urine appears dark and yellow (if your urine is dark, misty and has an odour, you are dehydrated!)
  • Not producing tears
  • Sunken eyes
  • Lethargic or comatose (with severe dehydration)
  • Headache
  • A lack of sweating.

If you have ever woken up after a heavy night on the town with a headache, then you are familiar with the symptoms! Alcohol causes dehydration which in turn leads to a hangover and results in that banging headache.A physical examination may also show signs of:

  • Low blood pressure
  • Blood pressure that drops when you go from lying down to standing
  • Rapid heart rate
  • Poor skin turgor – the skin may lack its normal elasticity and sag back into position slowly when pinched up into a fold by the Doctor; normally skin springs right back into position
  • Delayed capillary refill
  • Shock.


To avoid becoming dehydrated, drink plenty of water at regular intervals. Aim to replace fluids at the same rate that they are lost, so little and often is ideal.

A good indication that you are well hydrated is the frequency of toilet visits and the colour of your urine. If you are urinating frequently and your urine is clear and odourless then you are sufficiently hydrated.

It is important to carefully monitor someone who is ill, especially an infant, younger child or older adult. If you believe that dehydration is developing, consult a Doctor before the person becomes moderately or severely dehydrated. Also, begin fluid replacement as soon as vomiting or diarrhoea start. DO NOT wait for the signs of dehydration! The easiest signs to monitor are urine output, saliva in the mouth and tears in the eyes.

Even when you are healthy, drink plenty of fluid every day. Drink more when the weather is hot or when you are exercising.

Important Note: Do not rely on thirst to tell you, you will be dehydrated before then!

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