Environmental Engineering Reference
In-Depth Information
The use of some chemical strippers may result in exposure to volatile vapors
which may be quite toxic (e.g., methylene chloride). As a consequence, the
use of such strippers is undesirable. Chemical stripping usually leaves some
lead on painted substrates.
v. Vacuum and water blasting. Blasting methods are used to remove
paint on exterior surfaces such as building cladding. Both vacuum and water
blasting methods produce significant waste and are very expensive. Vacuum
blasting subjects a surface to bombardment with abrasive materials that are
captured along with lead dust by means of a HEPA vacuum. It can be used
on a variety of surfaces but works best on flat surfaces. Both methods can
damage the treated surface.
C. Biological contaminants
A variety of source control techniques are used to prevent and mitigate
building-related health problems associated with biological contaminants.
This is true for Legionnaires' disease; hypersensitivity pneumonitis/humid-
ifier fever and similar exposure problems; hospital-acquired infections;
asthma and allergy symptoms associated with exposure to dust mites, cock-
roach, pet, and mold allergens; and other microbially produced contaminants
such as mycotoxins, endotoxins, and microbial VOCs.
1.
Legionnaires' disease
Prevention of outbreaks of Legionnaires' disease and mitigation of exposure
problems once they have become manifest requires an understanding of
environmental conditions that result in proliferation of the disease-produc-
ing organism,
Legionella pneumophila
, its dispersal, and techniques that are
effective in its control.
Outbreaks of Legionnaires' disease can be avoided. Warm water envi-
ronments (>86° <140°F, >30°
.
Outbreaks or sporadic cases of Legionnaires' disease have been reported for
mechanical draft cooling towers, evaporative condensers, whirlpool spas,
hot tubs, and hospital hot water heating systems. Such systems are at risk
of serving as reservoirs for significant
<60°C) favor the growth of
L. pneumophila
population growth. It
is therefore incumbent on facilities management to review its use of such
systems and O&M practices.
L. pneumophila
One approach to reducing the potential occurrence
of Legionnaires' disease is to abandon the use of mechanical draft cooling
towers and evaporative condensers. Many hospitals in the U.S. no longer
use mechanical draft cooling towers because of risks to immunocompro-
mised patients. Another approach is to upgrade older cooling towers by
installing more efficient mist eliminators. Newer systems have significantly
lower emissions (17 to 20%) of aerosolized water than older cooling towers.
Hospital guidelines in the United Kingdom recommend replacement of wet
a.
Cooling towers.
