INDOOR AIR QUALITY UK

 

 

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IAQ UK is an independent organisation with the aim of 'raising the agenda of indoor air quality within the home and workplace'

IAQUK Resources - Temperature

Thermal Responses

 

Individuals essentially use two methods to ensure we maintain an optimum core temperature:

 

  • Thermoregulatory Response
  • Autonomic Physiological Response

 

Thermoregulatory Response

 

Achievement of optimum body temperature is achieved firstly by behavioral response to self regulation of thermal comfort.  Such thermoregulatory responses typically include:

 

  • Modifying clothing insulation
  • Altering the environment thermostat
  • Opening a window
  • Drinking a temperature drink
  • Using mechanical aids, such as fans or heater
  • Splash water on body to cool down
  • Adjust work rate

 

Autonomic Physiological Response

 

Where such adjustments are not possible or as effective, autonomic physiological responses are involuntary employed by the body’s defense mechanism.  These include:

 

  • Our skin vessels dilate in heat to assist with redistributing warm blood from the core of your body to the body surface to help increase dry heat loss (convection).
  • We also sweat to facilitate the evaporation of heat loss (conductivity). Sweating usually begins when the body’s temperature rises above 36.7°C. 
  • When the body temperatue cools, the body responses by shivering. This is called shivering thermogenesis, when muscle groups contract and relax in small movements which result in creating warmth by expending energy.
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Health effects


Cold

 

  • Discomfort, shivering, fatigue, loss of motor co-ordination.
  • Severe exposure can cause white finger and possible frostbite.

 

Heat

 

  • Discomfort, sweating, flushed skin, fatigue, dizziness, muscle cramps, nausea, vomiting, dehydration, skin conditions and excessive or erratic pulse.
  • Severe exposure: can cause heat stress and heat stroke
  • Uncomfortable exposure can lead to loss of concentration, reduction in capacity and efficiency.
  • Heat may also affect contents within the building, as an example servers can often be sensitive to high temperatures.

Thermal Comfort

 

The Workplace (Health, Safety and Welfare) Regulations 1992, Regulation 7 specifies ‘during working hours, the temperature in all workplaces inside buildings shall be reasonable.  The minimum temperature is 16°C formost types of work with a minimum 13°C where severe physical effort is used.  There is currently no maximum temperature limit, although work unions have called for a maximum working temperature of 30°C, or27°C for those doing strenuous work.

 

According to the British Standards BS EN ISO 7730 the term thermal comfort is a ‘state of mind that expresses satisfaction with the surrounding environment’.  Therefore thermal comfort is a subjective matter. The Health & Safety Executive recommend that employers should adopt a ‘reasonable comfort’ standard; quoting 80% of the workforce should be ‘thermally comfortable’.

 

The Health & Safety Executive previously defined thermal comfort ‘between 13°C (56°F) and 30°C (86°F), with acceptable temperatures for more strenuous work activities concentrated towards the bottom end of the range, and more sedentary activities towards the higher end.'  The World Health Organisation (WHO) recommends a maximum temperature of 24°C for comfortable working, which is different to safe working.

 

The average body core temperature is 37°C with a skin temperature of 32-33°C; which is quite a bit higher than the ambient (surrounding) temperature in most workplaces. Volatile Organic Compounds (VOC) is a collective term given to a variety of chemical compounds that vaporise under normal conditions entering our indoor environment.  It is considered that about 350 different types of VOCs are present in our indoor environment.

Vulnerable People


Some individuals can be more vulnerable to temperature changes, including elderly, very young, and those convalescing. Certain conditions can increase vulnerability (Cardiovascular and cerebrovascular, obesity/ malnutrition, respiratory conditions).  Medication may also inhibit an individual’s thermoregulation. (Neuroleptics, Serotoninergic agonists, Anti­cholinergics, Vasoconstrictors, anti­hypertensives).

 

Pregnant woman are more susceptible to heat intolerance, as hormonal changes increases metabolism and core body temperature, particularly around second and third trimester.  The additional weight carried during pregnancy expels further energy, thus stimulating heat. Breast feeding women are susceptible to becoming more dehydrated in hot conditions.

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Thermal Energy Transfer

 

Thermal energy can transfer through an environment from a hot source to a cold source, using three methods:

 

  • Conduction
  • Convection
  • Radiation

 

Conduction

Conduction is the transfer of heat via substances that are in direct contact with each other.  The better the conduct the more rapidly the heat will transfer.  As an example metal pipes carrying hot water.

 

Convection

Convection moves energy via gases and liquids. As liquid or gas heat, it expands, causing movement. An example, steam from a hot water, or cold chilled air to cool a room or refrigerant.

 

Radiation

Electronic waves traveling through the atmosphere is called radiation.  When the electronic waves come in contact with an object, it transfers its heat.  As an example the sun’s solar energy.

 

Such methods are relevant when monitoring or risk assessing source of temperatures and transfer within an environment.

Monitoring

 

When monitoring avoid direct sunlight, wind, thermal radiation, heating or ventilation ducts, or other such conditions.  Obtain data for hot and cold areas as well as general areas and monitor in consistent locations to provide comparison changes/fluctuations.  If possible, compare findings with existing reports, including any mechanical ventilation system reports.

 

There are primarily two methods for monitoring temperature:


 

Digital thermometers

 

  • Ensure calibrated.

  • Only use infra-red thermometers for surface temperatures.

  • Read the instrument’s instructions carefully.

  • Surface temperature readings are different to air temperatures. The further away from the surface the device is held, the larger the area of measurement is causing a potential error.

 


Dry Bulb Mercury Thermometers

 

  • Allow sufficient time of 2-3 minutes for the thermometer findings to stabilize.

  • Hold the thermometer upright and take a reading straight on.



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However it is not just the environment that affects an individual’s core temperature or their perception of thermal comfort.

 

High levels of carbon dioxide complicate the body’s ability to self regulate.  Carbon dioxide can suppress shivering, it can cause confusion for an individual to accurately gauge the ambient temperature, and it can also increase blood flow which consequently raises body temperature. At high humidity the body is less effective of losing heat through conductivity (sweating).  This is due to the amount of vapors in the air, reducing evaporation from our skin.

 

Eating a large meal can increase your core temperature and cause sweating.  This is called diet-induced thermogenesis when your body has to generate more energy to digest the meal.

 

Exposure to frequent changes to temperature, effects the body’s ability to respond, such as sitting near a draft, fans, ventilation exchanges, solar energy (sunlight) from sitting near windows, moving around different temperatures within the workplace (outside to indoors). The pace of your work activity and physical labour required can create core temperature from energy expelled.

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Technical Reference


 

Statutory requirement

 

  • Minimum 16°C for most types of work
  • Minimum 13°C where severe physical effort is used

 

Recommended


  • Recommended safe temperature - 13°C and 30°C
  • Recommended comfortable temperature - maximum  24°
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Best Practice

 

Policy

With buildings becoming more energy efficient and the environment controlled mechanically, reducing the control the occupant has over their thermal comfort, often relates to a difficult quest for the facilities management team to find an optimum working condition.  Therefore good practices would adopt a comfort working temperature parameter policy for thermal comfort, that is realistic and achievable.

 

Continuity Plan

Thermal comfort may be compromised by extrinsic matters, such as during period of power loss, or extreme weather conditions.  A continuity plan will assist with direct action to maintain thermal comfort during, such as portable thermal devices, breaks, clothing and access to hot/cold drinks.

 

Consultation

Consult with employees about suitability and what is achievable, discuss parameters for temperature ranges and what action employers will take if these parameters are exceeded.

 

Risk Management

An employer must take reasonable care to identify any foreseeable health or safety hazards, which could harm the employee or other persons in the workplace. The hazards may involve work practices and systems, people, equipment, materials and environment.

           

Identify the risks

Consult with occupants

Conduct monitoring

Identify potential thermal sources

Identify thermal transfer

 

Assess the risk

Number of people involved

Vulnerability of people

Work practices and work rate

Type of plant, equipment or materials used

The capability, skill, experience and age of people doing the work

 

Control the risk

Eliminate or control the risks as reasonably practicable using hierarchy of controls.

 

Monitor and Review

Monitor and review as required by your risk assessment.

 

Occupants should be consulted when assessing the potential risks from exposure to hot or cold conditions. Employees must also have input into the risk controls selected.

Checklist

 

Factors to consider when risk assessing temperature within the workplace:

 

  • Are there any high or low temperature hot spots?  Are these due to the occupants using fans or heaters?  Has new equipment been installed?  Has this interference affected the thermostat?
  • Are occupants exposed to energy from machinery or solar energy from windows?
  • Are the occupants exposed to drafts, ventilation diffusers? Can you isolate the source or move the occupant?
  • Is there any difference between floor to ceiling temperature gradients?  The difference should not exceed 3°C.
  • Are the thermostats functioning and calibrated?  Are they correctly located away from temperature sources?  Do they control the rooms indicated? 
  • Does the air distribute a balance circulation? Do occupants use fans?
  • Are there any obstructions to the air circulation, such as office partitions, cabinets, display stands etc?
  • Consider the occupants, such as vulnerable people and individuals health conditions or medication that may influence thermal comfort.
  • Explore the work rate within the environment, could this influence core body temperature? Are employees working in extreme temperatures allowed to take suitable breaks? Wear suitable personal protective clothing? Access to fluid replacement when subject to dehydration?
  • Are there areas of overcrowding increasing thermal heat?
  • Are there any complaints, occupational health referrals or incidents resulting from thermal conditions?
  • What temperature transfers methods are employed which may affect the thermal comfort?  (uninsulated hot water pipes, solar energy etc)
  • Are plant, service lines, walls, floors and roofs insulated?
  • Are extreme thermal sources removed from exhausts or other sources to outside the building?
  • Are staff consulted about working temperatures?  Do staff receive training about reporting thermal discomfort?
  • Do you employ regular monitoring activities and document findings?  Do you have a competent person to conduct such monitoring activities?

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