Microclimate

Microclimate measurements

Microclimatic comfort is essential in all workplaces and public places. To obtain good microclimatic conditions it is necessary that they are acceptable both from the point of view of the thermo-hygro-anemometric parameters that characterize the microclimate, and the levels of illumination and air quality.

A comfortable microclimate is what inspires in most people a feeling of satisfaction with the environment, identified with the term “hygrothermal well-being” or simply “comfort”. Microclimatic factors at the workplace, together with the intensity of physical activity and clothing, cause in humans a series of biological responses ranging from feelings of Hygrothermal well-being to feelings of discomfort, from a serious effort for thermoregulation (more or less pronounced sweating) to pathological syndromes (heat stress).

A microclimate problem, such as discomfort, arises from both the global perception of the human body and by localized annoying situations and can be essentially reduced to sensations of heat, cold, or excessive air flow or thermal shock.

MICROCLIMATE EVALUATION

 

LABORAD srl performs microclimate risk assessments to determine the comfort of employes or of those who stay in a specific environment according to current laws (D.Lgs. 81/08 and technical standards). Our technicians are equipped with microclimate control units with specific probes and software that allow to make an assessment of the specific microclimate for each work task considering the energy expense and the type of clothing. The evaluation of comfort of workers and microclimate at the workplace is done measuring the environmental and individual parameters and then analyzing thermal comfort indices that allow to quantify the microclimatic conditions of an environment according to the workers (hot/comfortable) and their possible thermal discomfort (PMV = Predicted Mean Vote and PPD = Predicted Percentage of Dissatisfied).

Moreover, the analysis carried out by the microclimate control unit is able to provide the lines of intervention that allow to overcome any problems of microclimatic discomfort.

To complete the microclimate risk assessment, our technicians perform lightning measurements and controls of indoor air quality for chemical pollutants (asbestos, carbon dioxide, carbon monoxide, Radon) and microbiological ones (Legionella spp, molds, yeasts…), and provide solutions to achieve requirements for the workplace (D.Lgs. 81/08. Title II, Chapter I).

 

MICROCLIMATE IN THE WORKPLACE

The measurement of the microclimate in the workplace begins to gain an important role in the Document of hazard evaluation for companies. For a global assessment of the hazards present in the offices of public administrations, businesses and private companies ISPESL guidelines are available (in italian):

www.ispesl.it/linee_guida/pubblica_amministrazione/amm2.htm
www.ispesl.it/linee_guida/pubblica_amministrazione/amm4.htm#all
www.ispesl.it/linee_guida/tecniche/LGMicroClima062006.pdf

In the other cases, when evaluating microclimatic hazards, it is of crucial importance to distinguish between environments in which there are specific thermoigrometric needs for production and those in which this does not apply.

For the analysis of microclimate there are:

  • moderate environments, with conditions similar to the optimum for the human body;
  • severely hot environments and severely cold environments, where specific and unavoidable productive needs determine the presence of high or low temperatures..

The vast majority of workplaces falls into the first category; in the second class fall environments in which is impossible to properly control microclimate, such as operation near ovens, refrigerated rooms but also operating rooms…

Anyway, in both classes of environments a serious evaluation of microclimatic hazard must be performed with proper instrumental measurements.

MICROCLIMATIC UNIT

LABORAD srl’s technicians are equipped with a microclimatic unit made for the study, the measurement and the assessment of microclimate in the workplace.

The instrument is able to visualize and register at the same time the measurements of environmental microclimatic factors such as: Temperature with dry bulb, Temperature with wet bulb, Globothermometric temperature, Relative humidity, Airflow. The unit is also able to calculate directly the WBGT indexes for indoor and outdoor environments and to measure the vertical discomfort (drafts at floor level, vertical thermal gradients) and radiant asymmetries.

The specific software allows to do an analysis of the recorded microclimatic parameters allowing to simulate their variation and instantly verify the effect of the variation on comfort perception and thermal comfort indexes.

THERMAL COMFORT INDEXES

Thermal comfort is defined by ASHRAE (American Society of Heating, Refrigerating and Air Conditioning Engineers INC) as a condition of psico-physical wellbeing of the individuals in the environment in which they live and work.

The evaluation of this state can be quantified using integrated indices that consider both environmental microclimatic parameters (Ta, Tr, Va, RH), and the energetic cost (metabolic cost MET) of the work activities, and also the type of clothing (thermal insulation CLO) commonly used.

Among the indices, the one that identifies the influence of physical and physiological variables on thermal comfort is the PMV (Predicted Mean Vote). It derives from the equation of thermal balance, whose result is rapported to a scale of psychophisical wellbeing and expresses the mean vote of the thermal feelings of a sample of individuals in the same environment.

From PMV derives a second index, named PPD (Predicted Percentage of Dissatisfied) that quantifies the percentage of “not satisfied” individuals about specific microclimatic conditions.

The technical standard UNI EN ISO 7730:2006 suggests for a condition of thermal comfort PMV values between + 0,5 and – 0,5, corresponding to a PPD under 10%.

PMV

PPD %

ASSESSMENT OF THERMAL ENVIRONMENT

+3

100

Very hot

+2

75,7

Hot

+1

26,4

Mildly hot

-0,5< PMV <+0,5

< 10

Thermal wellbeing

-1

26,8

Mildly cold

-2

76,4

Cold

-3

100

Very cold

PMV index is particularly good to evaluate workplaces with a moderate microclimate, such as homes, schools, offices, research laboratories, hospitals, etc.; it is useful also to identify mild levels of discomfort in those environments.

LEGISLATION

D. Lgs. n.81 of 09/04/2008 (annex IV point 1.9 Microclimate): Implementation of article 1 of law 3 august 2007, n. 123, regarding health and safety in the workplaces.

Technical Standard

– UNI EN ISO 7730:2006
Ergonomics of the thermal environment – Analytical determination and interpretation of thermal comfort using calculation of PMV and PPD indices and criteria for thermal comfort.

– UNI EN 27243:1996
Hot environments. Evaluation of heat stress to humans in the workplace, based on the WBGT index (wet bulb and globe thermometer).

– UNI EN ISO 7933:2005
Ergonomics of the thermal environment – Analytical determination and interpretation of heat stress using calculation of the predicted heat strain

– UNI EN ISO 8996:2005
Ergonomics of the thermal environment – Determination of energetic metabolism

– UNI EN ISO 7726:2002
Ergonomics of the thermal environment – Instruments for measuring physical quantities.

– UNI EN ISO 11079:2008
Ergonomics of the thermal environment – Determination and interpretation of thermal stress from cold with the use of thermal insulation required clothing insulation (IREQ) and local cooling effects.

Guidelines (in italian)

•  Microclima, aerazione e illuminazione nei luoghi di lavoro. Requisiti e standard. Indicazioni operative e progettuali.

•  Linee guida microclima qualità dell’aria e inquinanti indoor_Linee guida min sanità