INERGEN: Summary of Relations, Physiologic Factors and Fire Protection Engineering Design

Rubicon Research Repository/Manakin Repository

INERGEN: Summary of Relations, Physiologic Factors and Fire Protection Engineering Design

Show full item record


Title: INERGEN: Summary of Relations, Physiologic Factors and Fire Protection Engineering Design
Author: Lambertsen, CJ
Abstract: This summary is derived from existing physiologic and performance data relating to exposures to lowered inspired oxygen, and to increased inspired carbon dioxide partial pressures. All of the referenced data are based on direct measurements in human subjects. The relevant research and analysis concerning tolerance to, and advantageous physiologic roles of, carbon dioxide in hypoxia cover the fifty-year period, 1943-93. Two types of individuals have been considered in relation to physiologic factors in the practical operational use of INERGEN. They are (a) normal healthy individuals and (b) workers who have returned to work after therapy for a clinical medical handicap. Normal individuals can be considered for both brief exit and for the possibility of more extended exposures to INERGEN fire preventive or extinguishment procedures.Information provided concerning normal individuals is extensive, covering the cited over-fifty years of detailed research (9, 18,19 ,34,42,48). Clinical medical specialists have evaluated situations relating to active workers who have residual medical handicaps. These evaluations have been provided as informed judgements by highly qualified clinical specialists and scientists, based on related clinical medical experience and on clinical research involving hypoxia or exercise tolerance examinations. To exit the protected zone, medically handicapped individuals require only the basic capacity and adequate time to do so. Throughout all aspects of the cited research it has been recognized that the occurrence of a detectable and harmless advantageous physiologic effect, or the occurrence of a demonstrable adverse effect, is dependent upon both the degree and the duration of an associated hypoxia and hypercapnia. Small degrees of hypoxia and hypercapnia can be tolerated for several days without detectable adverse effect (7). The most severe degree of either hypoxia or hypercapnia can be tolerated for less than one minute (15, 18, 19). Between these extremes are degrees of combined hypoxia and hypercapnia, which are advantageous both to safety and effectiveness for durations important in fire protection applications (1 ,7,9, 19,42,48,49). In the practical considerations of fire protection scenarios, a distinction is made between (a) INERGEN use, (b) physiologic effects, and (c) effects of fire, heat, or toxins in smoke produced by combustion. Recognition is given to the normal desirability of routine prompt exit from spaces when fire is actually occurring, regardless of the extinguishment agent used. The duration of safe tolerance to products of combustion (toxins) will be very much less than the physiologic tolerance to the non-toxic INERGEN component gases ( 48). INERGEN use in a fire extinguishment situation therefore does not impose a special (or exceptional) exit requirement. Moreover, in the event of unavoidable delay in exit, the reserve physiologic tolerance to INERGEN systems atmospheres provides enhancement of prospects for human survival without residual effect. No toxicologic basis exists for delay in initiating operational flooding with INERGEN. The earliest desirable activation of the system and consequent rapid fire suppression reduces the formation of respirable toxic products of fire (including smoke, N02, CN, and CO), as well as providing some dilution of an initial toxin formation. In situations of greatest risk from fire itself, the system engineering design specifications should be made to provide an extinguishing atmosphere that does not produce important adverse effects in normal persons. During a fire in an essentially closed space, individuals within the space should be considered safer with, rather than without, the use of INERGEN in its design concentration range for fire extinguishment. This applies both to a normal exit period and to an unexpected requirement for delay in exit after activating the system during a fire situation. The several natural component gases of INERGEN are either inert or physiologically active, and not themselves toxic (18,48). It is established that carbon dioxide in the concentrations generated by INERGEN action (usually 5% or less) in a fire situation promptly improves tolerance to even severe degrees of hypoxia (9,42). It does this by preventing a decrease in the normal level of carbon dioxide in the lungs and arterial blood. This key to the importance of carbon dioxide in improving tolerance and safety in hypoxic atmospheres is the result of a composite of effects produced by three normal physiologic control mechanisms, which are dependent upon carbon dioxide. These include (a) stimulation of respiration, which increases arterial blood oxygen content and partial pressure, (b) dilation of brain blood vessels, which increases brain blood and oxygen flow, and (c) a shift in the hemoglobin oxygen dissociation curve, which aids unloading of oxygen in all tissues (9,17,48). All of these desirable and intrinsic natural effects occur with any tolerable degree of increased inspired carbon dioxide, and in any tolerable degree of hypoxia (9, 17, 19 ,27). An optimized improvement in hypoxia tolerance depends upon balancing the degree of increased carbon dioxide, the degree of atmospheric hypoxic exposure, and the tolerance to sensations produced (48). Intolerance to the INERGEN atmosphere in its design range is unlikely. Sensations would be related largely to any discomfort of respiratory stimulation, resembling that of mild exercise, which may tend to be erroneously called and considered "breathlessness." The feeling of excessive breathing, and headache if it occurs, is neither serious nor lasting. Any headache occurrence is considered an expression of brain vessel dilation, which itself is a desirable physiologic mechanism in adapting to hypoxia.
Description: The items forming the Rubicon Research Repository Christian J. Lambertsen collection are generously donated by the Lambertsen Family. All items in this collection are released through Creative Commons Attribution + Noncommercial + ShareAlike (BY-NC-SA) licenses in an attempt to encourage the use of these works to further scientific understanding of physiology.
URI: http://archive.rubicon-foundation.org/10581
Date: 1994

Files in this item

Files Size Format View
ocr_1994-04-14_ ... Physio-Fctrs-Fire-Prot.pdf 13.13Mb PDF View/Open

This item appears in the following Collection(s)

Show full item record

Browse

My Account