Traditionally, ventilation and air conditioning ducts have been manufactured with rectangular cross sections. The rectangular duct can easily be adapted, e.g. to restricted ceiling voids and plant rooms, however, often at the cost of efficient airflow design and possible cost savings. A round duct system normally performs better and offers a more economical solution, which is the reason why it always pays to study and compare the ductwork design before selecting which type is to be used for a specific application.

All internal combustion engines produce exhaust gases containing noxious compounds: carbon monoxide (CO), nitrogen oxides (NOx, carbon oxides (CxHy) and smoke. With the help of a mathematical model the concentrations of some dangerous substances at the end of the tunnel were calculated, and were replaced by a criteria! number. A corresponding computer program was also developed thus enabling quick and simple calculations of some concentrations and the criteria! number.

The terrifying organisms that live in our ventilation systems have perfected their methods of attack, but Martyn Love thinks he might have the answer          

This Update discusses the various factors that affect sound transmission through different types of concrete block walls, including single-leaf walls, double-leaf walls and walls with gypsum board attached. Knowledge of these factors will assist construction practitioners to design and build walls with high levels of acoustic performance economically.

This Update examines various fire-stopping techniques that meet the intent of the National Building Code of Canada (NBC) with respect to fire resistance and that do not adversely affect the sound isolation of the wall assembly. The information is derived from the results of an industry-sponsored consortium project led by the National Research Council's Institute for Research in Construction (IRC).      

This American National Standard describes procedures for the measurement of sound pressure levels in the outdoor environment, considering the effects of the ground, the effects of refraction due to wind and temperature gradients, and the effects due to turbulence. This standard is focused on measurement of sound pressure levels produced by specific sources outdoors. The measured sound pressure levels can be used to calculate sound pressure levels at other distances from the source or to extrapolate to other environmental conditions or to assess compliance with regulation.