Miller Magazine Issue: 116 August 2019

82 ARTICLE MILLER / AUGUST 2019 cessful fumigation but also to determine the leakage degree of the fumigation structure with regard to peo- ple’s safety. Table 1 shows the recommended rang- es of half-times for various applications. Half-life time pressure decay below those times, fumigation is not recommended. Half-life time pressure decay test is carried out by applying a positive or negative pressure for rigid structures but for flexible structures such as fumigation “bubbles” it is carried out only by applying negative pressure. To measure the pressure, fumiga- tor must use a differential pressure gauge. Half-life time pressure decay test would not produce meas- urable levels under tarpaulin fumigation, whether the commodity is in bulk or in stack. Table 1 - Provisional recommended ranges for var- iable pressure test carried out in structures destined for gaseous treatments to control storage insects. Gas monitoring Fumigator must monitor gas leaks with a personal safety gas detector device. Most common safety de- vices that are in the market today detect phosphine and MB at a range of 0-20 ppm. In most parts of the world. Threshold Limit Value (TLV) of phosphine in some counties is 0.1 ppm and for MB TLV is 1 ppm. Above these values, devices will alert the user (Bond, 1984). Today, there are also on-line monitoring de- vices which transmit a signal if concentration outside the fumigated structure exceeded its defined limits. In any fumigation, at least two people must be pres- ent, where one of them has to be a certified fumigator equipped with a personal gas detecting device. Before fumigation, after all sealing has been done and before introducing the fumigant, fumigator must make sure there are life lines in case of an emergen- cy. All fumigation structures must be properly posted with warning signs at eye height from all directions according to the local legislation. Automatic gas monitoring warning system A very modern automated system for people safety was recently presented by Centaur.ag and includes 2 levels of protection. The system contains multiple gas sensors reading low concentrations of phosphine, CO2 or Oxygen. The frequency of monitoring is set by the user. The first level of protection is the “safe to enter” barrier. The area manager allows workers to enter only when the green light is on. The second barrier is activated upon detection of unsafe condi- tions. The system then initiates a visual and sound alarm for people to exit the area and a warning red light by the door informs people not to entry. The system automatically starts aeration fans to clear the air. All actions are automatically recorded and reports are released. The current conditions and history are available in real time on the cloud for users with pass- word from every computer or smartphone. One of the strongest points of this system is that is based on many sensors. Even if one sensor fails, the rest will still maintain safety. When a person’s safety is based only on his personal meter, the risk of failure can be lethal. Photo 1: The setup of the automatic gas monitoring warning system Personal Protective Equipment All fumigant applicators (fumigators and operators) must be equipped with Personal Protective Equip- ment (PPE) according to fumigants’ labels. Different type of gloves is required for each fumigant. For ex- ample, since phosphine in its solid form sublimates to gas by reacting the moisture in the air (with water vapors) fumigation will require cloth gloves to avoid transfer of sweaty hands during summer (Annis and Graver, 1990). MB reacts with sulfur which is one of the components in rubber, therefore, rubber gloves for MB fumigation are not recommended (Graver, 2004). Since the mode of action of all fumigants is by in- halation, most important component of PPE is a respiratory mask under the category of Respiratory Protective Equipment (RPE). There are various types of masks; for short term exposure and low concentra- tions (phosphine <1%, <MB 2%) usually from minutes to hours (Graver, 2004). The simplest form of mask is a disposable respirator or a reusable half-face respi-