Planners should consider factors such as heat transmission, convection and the exchange of long-wave radiation in choosing the properties of materials, structural components and connections. This is especially important in and around joints, at the bonded edges of glazing and panels, and in the area of fastening elements because linear or intermittent thermal bridges and leaks can increase the risk of heat losses, condensation and mould formation. Water must not be allowed to penetrate structures in and around closed facade surfaces such as plastered masonrypunctuated facades and partitioned exterior wall structures like glass facades. Any water that does penetrate must be extracted in a controlled manner.
These problems have increased with the construction of buildings that are designed to be more airtight and that recycle air with a smaller proportion of Regulating the substance formaldehyde essay air from the outside in order to be more energy efficient.
The fact that buildings that do not offer natural ventilation present risks of exposure to contaminants is now generally accepted.
The term indoor air is usually applied to nonindustrial indoor environments: Concentrations of contaminants in the indoor air of these structures are usually of the same order as those commonly found in outdoor air, and are much lower than those found in air in industrial premises, where relatively well-known standards are applied in order to assess air quality.
Even so, many building occupants complain of the quality of the air they breathe and there is therefore a need to investigate the situation. Indoor air quality began to be referred to as a problem at the end of the s, although the first studies did not appear until some ten years later. Although it would seem logical to think that good air quality is based on the presence in the air of the necessary components in suitable proportions, in reality it is the user, through respiration, who is the best judge of its quality.
This is because inhaled air is perceived perfectly through the senses, as human beings are sensitive to the olfactory and irritant effects of about half a million chemical compounds. Consequently, if the occupants of a building are as a whole satisfied with the air, it is said to be of high quality; if they are unsatisfied, it is of poor quality.
Does this mean that it is possible to predict on the basis of its composition how the air will be perceived? Yes, but only in part.
This method works well in industrial environments, where specific chemical compounds related to production are known, and their concentrations in the air are measured Regulating the substance formaldehyde essay compared with threshold limit values. But in nonindustrial buildings where there may be thousands of chemical substances in the air but in such low concentrations that they are, perhaps, thousands of times less than the limits set for industrial environments, the situation is different.
The situation is comparable to what happens with the detailed composition of an item of food and its taste: For this reason, when a ventilation system and its regular maintenance are being planned, an exhaustive chemical analysis of indoor air is rarely called for. Another point of view is that people are considered the only sources of contamination in indoor air.
This would certainly be true if we were dealing with building materials, furniture and ventilation systems as they were used 50 years ago, when bricks, wood and steel predominated.
But with modern materials the situation has changed. All materials contaminate, some a little and others much, and together they contribute to a deterioration in the quality of indoor air. These are illustrated in figure Although poor indoor air quality results in fully developed illness in only a few cases, it can give rise to malaise, stress, absenteeism and loss of productivity with concomitant increases in production costs ; and allegations about problems related to the building can develop rapidly into conflict between the occupants, their employers and the owners of the buildings.
In addition, for many contaminants present in the air, the effects of acute exposure are well known, whereas there are considerable gaps in the data regarding both long-term exposures at low concentrations and mixtures of different contaminants. The concepts of no-effect-level NOELharmful effect and tolerable effect, already confusing even in the sphere of industrial toxicology, are here even more difficult to define.
There are few conclusive studies on the subject, whether relating to public buildings and offices or private dwellings. Series of standards for outdoor air quality exist and are relied on to protect the general population. They have been obtained by measuring adverse effects on health resulting from exposure to contaminants in the environment.
These standards are therefore useful as general guidelines for an acceptable quality of indoor air, as is the case with those proposed by the World Health Organization.
Technical criteria such as the threshold limit value of the American Conference of Governmental Industrial Hygienists ACGIH in the United States and the limit values legally established for industrial environments in different countries have been set for the working, adult population and for specific lengths of exposure, and cannot therefore be applied directly to the general population.
Another aspect that should be considered as part of the quality of indoor air is its smell, because smell is often the parameter that ends up being the defining factor. Smell is therefore very important when defining the quality of indoor air. While odours objectively depend on the presence of compounds in quantities above their olfactory thresholds, they are very often evaluated from a strictly subjective point of view.
It should also be kept in mind that the perception of an odour may result from the smells of many different compounds and that temperature and humidity may also affect its characteristics. From the standpoint of perception there are four characteristics that allow us to define and measure odours: The attempt to mask bad odours with good ones usually ends in failure, because odours of very different qualities can be recognized separately and lead to unforeseeable results.
It is evidenced by a variety of physical and environmental problems associated with non-industrial indoor environments. The most common features seen in cases of sick building syndrome are the following: Thus, ventilation is cited as an important contributory factor in the majority of cases.
Another question of a different nature is that of building-related illnesses, which are less frequent, but often more serious, and are accompanied by very definite clinical signs and clear laboratory findings. Examples of building-related illnesses are hypersensitivity pneumonitis, humidifier fever, legionellosis and Pontiac fever.
A fairly general opinion among investigators is that these conditions should be considered separately from sick building syndrome. Studies have been done to ascertain both the causes of air quality problems and their possible solutions. In recent years, knowledge of the contaminants present in indoor air and the factors contributing to a decline in indoor air quality has increased considerably, although there is a long way to go.Japan's regulations and environmental law Air Pollution Related links to Japan's regulations, Environment Law.
The Basic Environment Law and the Basic Environment Plan. The substance, which can be synthesized more efficiently in a factory, is about 3, times sweeter than sugar and supposedly does not have the unpleasant aftertaste that most current stevia extracts have.
Contents. Imprint Table of contents Foreword 4 5 6. Shell, wall, facade – an essay 8. Part A The fundamentals 1 External and internal conditions 2 General basics of construction Surfaces. As of October 6th, the CDPH archive site has been retired.
Click here to access our new website at regardbouddhiste.com Our archive site has been retired as of October 6th, You will be redirected in First Time or Infrequent Visitors. Food, substance consisting essentially of protein, carbohydrate, fat, and other nutrients used in the body of an organism to sustain growth and vital processes and to furnish energy.
The absorption and utilization of food by the body is fundamental to nutrition and is facilitated by digestion.
SCIENCE AND MORALS § 1. THE GOSPEL OF SCIENCE. In the days before the war the Annual Address delivered by the President of the British Association was wont to excite at least a mild interest in the breasts of the reading public.