Airflow check

Ventilation—air inlets and outlets should have unrestricted airflow. Check secnrity of duct work. Check operation of any motor-operated louvres. 

Daily and before-use inspections/tests. At a minimum, daily/before-use and quarterly inspection and testing should be conducted on fume hoods. The daily or before-operation inspection should consist of an airflow check. A simple qualitative check that can be used to check for proper airflow, exhaust, is the ribbon or tissue paper check. During this test, a ribbon or piece of tissue paper (be careful not to lose control of these for they could gum up the system) is placed at the hood opening to determine if it reflects directional airflow. Daily and before each use the hood gauges and monitors should be checked for proper operation within a predetermined range. 

Check for underventilation caused by obstructed vents, faulty dampers or other HVAC system malfunctions, or from problems within the occupied space. Furniture, papers, or other materials can interfere with air movement around thermostats or block airflow from wall or floor-mounted registers. If office cubicles are used, a small space (i.e., two to four inches) between the bottom of the partitions and the floor may improve air circulation. 

Simple Evaluation A simple evaluation can be done by checking the airflow rate into the opening, presuming the source characteristics, the placing of the exhaust, and the other parameters (cross-draft, work routines, supply airflow rate, etc.) have not changed since the detailed evaluation was done. It is necessary to do the simple evaluation at the same time as the detailed evaluation. The flow... 

It is necessary to check that no outward-directed velocity occurs across the open face of the booth. In such a case, another capture principle must be chosen or the exhaust airflow has to be increased until the needs are fulfilled. The possibility of spilling contaminated air out of the booth could also be reduced by the use of a flexible curtain covering the open face of the booth. 

Depending on use, the tighmess and containment of the box can be tested with a tracer gas or with generated contaminants. Since the pressure inside the box is lower than the pressure outside it could be easier to check the tightness without the exhaust airflow. Measurements similar to those for fume cupboards can be used. 

When open unidirectional airflow benches are being used in production sensitive to contamination, a thorough function check should always he carried out before the start of production. Studies of air movements with visual illustrative methods give both quick and valuable information. 

Contaminant concentrations Dispersal of airborne contaminants such as odors, fumes, smoke, VOCs, etc. transported by these airflows and transformed by a variety of processes including chemical and radiochemical transformation, adsorption, desorption to building materials, filtration, and deposition to surfaces evolution of contaminant concentrations in the individual zones air quality checks in terms of CO2 levels cross-contamination evaluation of zones air quality evaluations in relation to perception as well as health. Methods ate also applicable to smoke control design. 

Check that the airflow detector is not giving a false indication. 

Temperature and humidity is controlled to minimize evaporation of reagents and to keep performance of electronic equipment optimal. Ventilation is adequate for the removal of noxious fumes and odors. Formaldehyde and xylene vapor concentrations must be below maximum permissible levels. For formaldehyde, this level is 0.75 ppm for an 8-h time-weighted average, or 2.0 ppm for a 15-min short-term exposure. For xylene, the level is 100 ppm for an 8-h time-weighted average and 200 ppm for a 15-min short-term exposure. The monitoring of the work area and employees can be performed on a yearly basis. Chemical and biological safety cabinets are checked for proper airflow on a yearly basis. 

Check the firebox with an hydrocarbon detector (the plant s fire station will usually have one of these and someone trained in its use). Pay particular attention to stagnant areas of the firebox, as fuel-gas, valves tend to leak through burners and gases build up in areas of low airflow. Look for unburned gas and explosive mixtures. If you detect any such fuel or explosive mixtures, repeat step la or 16, then test again with the hydrocarbon detector. Continue this process until the firebox is purged of all combustible or explosive material. 

With TAi known and the air outlet temperature now estimated (TA2 = TAi + DTA), the log mean temperature DTM may be calculated. Refer to Table 5.1 for a review of DTM calculation. In the case of air coolers, the cold fluid is always the air side, which cools the process-side fluid. Ti is the process-side temperature and is always the highest of all the shown temperatures. Therefore, T - G should most likely be the greater temperature difference GTD. This is not true for every case, especially cases where there is limited airflow and therefore a large air-side temperature rise compared to other cases. You must therefore check to ensure you have chosen the correct temperature difference for these GTD and LTD values. 

Regularly check fume hoods for proper airflow. Ensure that fume hood exhaust is not drawn back into the intake for general building ventilation. 

A variant of the dynamic method may be, for example, an air conditioner of high accuracy that maintains the constant state of a sample placed in the airflow, which is kept at given T and y/ values [13]. Development of the equilibrium moisture content of the material is attained when the weight of the sample becomes constant. This may be checked by gravimetric measurements. 

Traditionally, the variation of evaporative rates across the stack has been counteracted by the installation of bidirectional fans and by periodically reversing the airflow direction through the stack. This policy has minimal effect on the drying rates in the center of the stack, but reduces the variation in behavior between the two end zones. If only moisture content variations are considered, many reversals are not needed to achieve this equalization (Pang et al., 1995 Nijdam and Keey, 1996 Wagner et al., 1996). However, if stress development in the surface layer with the likelihood of checking is taken into account, then the flow reversals for a timber such as Pinus sylvestris should be less than 2 h apart (Salin and Ohman, 1998). A period of 4 h is a common industrial practice for permeable softwoods such as P. radiata. 

The plant is run with as much airflow and sulphur feed as possible just a few days before the shutdown. All temperatures, SO2 % at inlet to converter and in exit gases, are checked. Airflow rate, pressure drop in each unit on gas side, and load on each motor are also checked. Any abnormality is noted down, and planning is started to correct it. 

If the airflow reading is doubtful, then check the temperature and SO2 % of exit gases from the furnace, operation of downstream units, and production rate of the plant. Check setting on metering pumps, current drawn by blower motor, temperatures of furnace and downstream converter passes, and rate of dilution water added, and correlate to material balance once a day/two days to estimate the loss of unreacted SO2 from stack. 

Additionally, to limit the buildup of contamination in the above designated areas, airflow is established to continually remove airborne contaminants. Airflows in the system are established at prescribed flowrates such that they are adequately filtered prior to being discharged to the environment. All air drawn from Zone 1 is exhausted through charcoal and HEPA filters to remove halogens and particulate contaminants from the exhaust air prior to release to the atmosphere. These ventilation filter systems are equipped with test ports and are periodically checked for operating efficiency. In addition to the ventilation system filters, in-box filtere are used to reduce the levels of airborne contaminants that are drawn into the Zone 1 ducting. 

Some easy ways to check for airflow are described in Section 7.1.4, but it is prudent to perform regular measurements to ensure proper fan operation. Anemometers are devices that measure wind velocity and a common form of this for lab use is a hot-wire anemometer, where the resistance of an exposed hot wire is measured. As air flows over the wire, it is cooled so one can measure flow rate by measuring resistance. The simplicity of this procedure is greatly compromised by the need for repeated measurements at many locations on the open faee of the hood. Thus, accurate measurements are not quiek and easy but with a good protocol, an average face velocity can be measured. An alternative... 

The isolator and gloves are tested daily for leakage. Airflow velocity if applicable is measured in-line with a calibrated instrument. The pressure inside the isolator is checked continuously. Furthermore, gas detection in case gaseous disinfection is used. 

In addition to the testing of the airborne concentrations of pollutants, it is necessary to check airflows and pressures created in a ventilation system to ensure that it is working to its designed performance by measuring ... 

Controls on underground diesel machinery generally involve correct tuning of the motors with frequent checks and adequate mine airflows in the operational areas. 

---