Goran Berndtsson
SEA Group, Safety Equipment America, Inc.
1001 Avenida Pico PMB #626,
Tel: +1-949-3023332
Fax :+1-714-8449137
e-mail:goran@sea.com.au
The efficiency,
performance and often life span of a filter respirator are affected by the
velocity and volume of the air flowing through the filter. Duration plays another important role. These
factors are often best expressed in the form of a breathing curve. However,
different breathing curves show different things. A good
understanding of breathing curves is essential to the respiratory protection
professional and makes it possible to glean more from the curve than seems
possible at a first glance. This
paper demonstrates the basic principles of breathing curves and some of the
major pitfalls in their interpretation. It presents
various types of curves and how to read what they show. The
paper explains the fundamental differences between volume and flow, and sets out
to form a basis for understanding data derived from breathing curves,
especially in relation to the velocity of the air traveling through a filter. The differences between continuous flow, as
used in many standards tests, and fluctuating flow, as occurring in normal
human breathing, are discussed, along with the effects of speech on the way we
breathe. Many
factors of great significance to respirator performance are directly
discernible from a careful look at the breathing curve.