SAFETY PRECAUTIONS 



Before Treatment 



Appropriate warning signs should be placed outside 

 of those areas where high C0 2 gas concentrations may 

 accumulate. Suggested wording for such a sign is: 

 "CAUTION -CARBON DIOXIDE GAS 

 Ventilate before entering. A high C0 2 gas 

 concentration may occur in this area. Carbon 

 dioxide gas interferes with breathing, and its 

 effects may be a hazard to life." 



During and After the Treatment 



C0 2 comprises 0.03 percent of the earth's 

 atmosphere and is indirectly the source of most of the 

 carbon of the organic compounds of our body. The 

 American Conference of Governmental Industrial 

 Hygienists 3 has set a threshold limit value for humans of 

 5,000 p. p.m. of C0 2 or 0.5 percent based on a 5-day, 

 35-hour or 40-hour work week. Any C0 2 escaping from 

 leaks in the equipment or facilities described here would, 

 in most cases, blend into the atmosphere, and 

 concentrations would quickly fall to within safe limits. 

 Because C0 2 gas is 1 -Vz times as heavy as air, it tends to 

 collect in unventilated areas, such as the working areas 

 below silo complexes. Areas such as these should have 

 air flowing through them during grain treatments with 

 this gas. 



C0 2 is the regulator of the breathing function in 

 vertebrates. An increase in the C0 2 inhaled will cause an 

 increased rate of breathing. A 2-percent concentration in 

 air will cause a 50-percent increase in respiration; a 5-per- 

 cent concentration will cause a laborious 300-percent in- 

 crease in respiration. 4 Therefore, treated storage facilities 

 should not be entered until after a sufficient time for 

 the C0 2 gas to diffuse into the atmosphere. This time 

 can be determined because analysis will show when 

 less than 0.5 percent of C0 2 is present in the air. 



If areas of high concentration of C0 2 must be 

 entered, self-contained breathing apparatus must be 

 used. Do not use air-breathing or filter-type gas masks. 

 Concentrations of C0 2 in grain can be rapidly removed 

 by running aeration fans, when present, or by turning 

 the grain; but, if the grain is to remain in store for some 

 time, it may be desirable to seal up the facility after 

 treatment and allow the concentration of C0 2 to 

 continue protecting the grain. 



Equipment 



Because the C0 2 is delivered as a liquid and is 

 stored in the tank at 300 p.s.i., it is advisable to use 

 caution when working on the delivery tank in any area 

 preceding the pressure regulator. Any work on the tank 

 should be performed by a serviceman from the company 

 from which the tank is leased. 



EQUIPMENT 



Application of C0 2 



The tank of liquid C0 2 should be obtained from a 

 distributor. The size of the tank will depend on the 

 amount of C0 2 to be used and the delivery schedule. 

 Currently, 2-, 4-, and 6-ton tanks are available. The tank 

 normally will be equipped with refrigeration to prevent 

 the liquid C0 2 from attaining too great a pressure and 

 with a small vaporizer to produce gas upon demand. For 

 treatment of grain, the small, built-in vaporizer is not 

 adequate for initial purges of large silos, elevators, or 

 tanks but will be adequate for subsequent treatments to 

 maintain the desired concentration of C0 2 . The built-in 

 vaporizer should be adequate for the initial purge and 

 subsequent treatments of small (500 to 10,000 bushels) 

 storage facilities. An external vaporizer will be required 

 for the initial purge of large storage facilities. It is 

 desirable to have two 57-ampere vaporizers, which are 

 similar to heaters, each capable of converting 600 

 pounds of liquid C0 2 to gas per hour. If adequate 



electrical power or equipment is not available, one 

 vaporizer of this size should be adequate for most 

 applications. A pressure regulator should be attached to 

 the final outlet of the C0 2 tank to reduce the tank 

 pressure (normally 300 p.s.i.) to 100 to 125 p.s.i. A 

 regulating valve (globe value) should be in the line after 

 the pressure regulator to maintain the desired flow rate. 

 A good quality 3/4-inch inside diameter rubber garden 

 hose may be used to introduce the C0 2 into the storage 

 facility. Rubber hose is more flexible than plastic hose at 

 reduced temperatures and, therefore, more desirable. 

 The hose should be long enough to reach into the 

 headspace of the facility and should be attached to the 

 tank at the regulating valve. 



Initial installation of the C0 2 tank vaporizers 

 and other equipment usually will be made by a service- 

 man or engineer from the company contracted to 

 supply the C0 2 . The tank is filled from a large trailer 

 truck capable of carrying about 30,000 pounds of 

 liquid C0 2 . 



3 American Conference of Governmental Industrial Hygien- 

 ists. Threshold limit values of airborne contaminants. Adopted 

 by ACGIH for 1969 and intended changes. 28 pp. 1969. 



'Anonymous. Matheson Gas Data Book. Ed. 4,500 pp. The 

 Matheson Company, Inc. East Rutherford, N.J. 1966. 



