Safe Use of Nontoxic Fumigants
Safe Use of Nontoxic Fumigants
Although gases such as nitrogen and argon are not pesticides, there are safety concerns about their use. Carbon dioxide is somewhat different. It is not con- ventionally considered a toxic material, but the presence of relatively small amounts in air causes breathing problems. Local regulations governing the use of carbon dioxide as a fumigant vary and should be ascertained by conservators
planning to use this gas for insect control. In Canada, for example, carbon diox- ide is not classified as a fumigant, and users do not have to be licensed. In Cali- fornia and in the United Kingdom, it is listed as a fumigant. In England, Rentokil
has gone through the necessary testing and documentation with the appropriate governmental authorities and is licensed to do carbon dioxide fumigation. No
Chapter 4 Chapter 4
OSHA literature warns that a drop in oxygen concentration as small as 1.4%, for example, from the normal 20.9% concentration in air to 19.5%, may start to have adverse effects on individuals. At 8-10% oxygen in nitrogen, the effect may be lethal. A general indication of what can happen with either nitrogen or
argon that is deficient in oxygen is shown in Table 4.2, which has been provided by the Compressed Gas Association. The indications are for a healthy, average
person at rest. Factors such as individual health, degree of physical exertion, and high altitudes can affect these symptoms and alter the oxygen levels at which they occur.
The Compressed Gas Association offers the following suggestions to individuals who may be subjected to oxygen-deficient atmospheres:
1. Never enter a suspected oxygen-deficient atmosphere without proper protective breathing apparatus and attendant support.
2. Analyze the atmosphere to determine if there is a deficiency of oxygen. Continue to monitor during the work process. If the oxygen level is less than 19.5%, ventilate to establish good air quality.
3. Be trained on what to expect and how to handle it.
4. Positively isolate to a confined area any incoming lines, and ventilate the area.
5. When it is necessary to work in any oxygen-deficient atmosphere, provide
a self-contained breathing apparatus or airline-style breathing mask for all workers.
6. Use an established hazardous-work permit procedure in all confined-space
activities.
Table 4.2
Safety concerns with oxygen-deficient
O xygen content
Effects and symptoms of acute exposure of humans
atmospheres.
(% by volume)
(at atmospheric pressure)
15-19%
Decreased ability to perform tasks. May impair coordination and may induce early symptoms in persons with heart, lung, or circulatory problems.
12-15%
Breathing rate increases, especially on exertion. Pulse rate up. Impaired coordination, perception, and judgment.
10-12%
Breathing increases further in rate and depth, poor coordination and judgment, lips slightly blue. At this oxygen content or less, anoxia will
bring about unconsciousness without warning—so quickly that individuals cannot help or protect themselves. Lack of sufficient oxygen may cause serious injury or death.
8-10%
Mental failure, fainting, unconsciousness, ashen face, bluish lips, nausea (upset stomach), and vomiting.
6-8%
8 minutes: may be fatal in 50-100% of cases; 6 minutes: may be fatal in 25-50% of cases; 4-5 minutes: recovery with treatment.
4-6%
Coma in 40 seconds followed by convulsions, breathing failure, death.
O perational Problems and Practices
A similar tabulation of physiological effects for carbon dioxide is provided in Table 4.3 (Banks and Annis 1990).
These safety factors are usually not an issue with anoxia treatments carried out with reasonable prudence in barrier bags. They come into play during operations involving large units placed in relatively tight quarters where many cylinders of gas or containers of liquid nitrogen may be used. The well-known
tendency of carbon dioxide to accumulate in low-lying and enclosed regions is a potential cause of safety hazards when high-level carbon dioxide atmospheres are used, particularly in leaky enclosures. A number of operators of carbon diox- ide chambers have installed monitors that are activated when levels of this gas rise from the normal 350 ppm in air to 1000 ppm. At this point, either a forced ventilation system is turned on or an alarm goes off. These are not uncommon occurrences. Because their density is similar to that of air, low-oxygen/high- nitrogen atmospheres are unlikely to present a similar type of hazard. All large chambers require adequate ventilation in the rooms in which they are used to
ensure that there is no external danger to personnel.
Table 4.3
Safety concerns with elevated carbon dioxide
Carbon dioxide content
Effects and symptoms of acute exposure of humans
concentrations in air.
(% by volume)
(at atmospheric pressure)
0.1-1% a
Slight increase in lung ventilation.
100% increase in lung ventilation.
Breathing becomes labored; maximum tolerable concentration for extended periods.
Upper limit of tolerance, with retention of consciousness for a few minutes.
Unconsciousness occurs within 1-2 minutes.
Rapid unconsciousness leading to death if person not removed within
a few hours. a OSHA time-weighted average of threshold limit is 0.50% or 5000 ppm.
Chapter 4
Chapter 5
This chapter, as well as chapters 6 and 7, presents down-to-earth detail about the work of individuals and institutions leading to the development of proce-
Anoxia Treatment dures for insect anoxia. The failures as well as the successes are recounted. A
snobbish conservator might call the tone terribly unsophisticated; this is true and
in Barrier-Film Bags it is intentional. A detailed and unvarnished history of actual experience in a new
field is far more helpful to most people entering it than the usual scientific article that glosses over crucial obstacles that may have taken years to overcome. The goal of this book is not only to disseminate rigorously proved data but also to
describe many varieties of practice, some perfected only after much experimen- tation and some still needing improvement, so that the conservator considering anoxia treatment will not have to reinvent the wheel.