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Ammonia Concentration Vs. Ventilation Rate
氨气浓度 VS 通风量
One of the biggest challenges with maintaining optimal air quality during cold weather is the fact that much of what we are trying to control is constantly being generated. For instance, if we had an empty house and filled it with smoke we could turn on a few exhaust fans and within minutes the smoke would be gone - problem solved. But, when it comes to gasses such as ammonia and carbon dioxide which are constantly being generated, it is a never-ending process to keep them under control. For example, during the minimum ventilation, “off cycle” ammonia levels will slowly rise as the ammonia produced by the litter builds. When the minimum ventilation fans turn on the ammonia levels will quickly decrease as fresh air is added to the house. But as soon as the exhaust fans turn off, the ammonia level will start to rise again and by the end of the “off cycle” it will be back to where it was prior to the fans turning on.
在寒冷季节维持鸡舍内最佳空气质量的最大挑战之一是我们试图控制的往往是产生问题的根源。举例来说，如果我们有一个鸡舍，里面充满烟气，我们可以打开几个排风扇，数分钟内浓烟会消失 - 问题解决了。 但是，当涉及到气体如氨气和二氧化碳，它们会源源不断的产生，控制这些气体是一个永无止境的过程。例如，在最小通风过程中，随着垫料慢慢潮湿，生成氨，风机停止时的氨浓度会慢慢上升。当最小换气扇打开时随着新鲜空气进入鸡舍，氨气水平会快速降低。但只要排气扇关掉，氨气水平将开始再次上升，并到风机停时它会回到之前风扇打开的水平。
Figure 1. Ammonia concentrations in broiler house between flocks The cyclic nature of ammonia concentrations in poultry houses can an be seen in Figure 1 where between flocks two 48' fans were operating three minutes out of every 30 to help limit the buildup of ammonia and moisture. Though operating the exhaust fans lowered the concentration of ammonia in the air by approximately 15 PPM, as soon as the fans turned off ammonia concentration started to rise, and within 30 minutes it was back to what it was before the exhaust fans turned on. The pattern continued for the next 14 hours of the study (Figure 2). Little if any progress was made in lowering the overall average ammonia concentration. 图1中可以看出禽舍中氨气浓度的周期性变化，其中在养殖期间时两个48英寸的风扇每30分钟运行3分钟以控制氨和水分的累积。 虽然排气扇运转降低了空气中的氨浓度约15 ppm，但是只要风扇一关氨浓度就开始上升，在30分钟内，它就会回到排气扇打开时的浓度。该模式在接下来的14个小时研究中一直保持（图2）。 在降低整体平均氨浓度上几乎没有进展。
The same cyclic pattern of ammonia concentrations can be seen in Figure 3 where minimum ventilation fans were operating 90 seconds out of five minutes in a house with three-week-old birds. Minimum fan operation decreased ammonia levels by approximately 7 PPM, but by the end of the minimum ventilation fan “off cycle” they rose the same 7 PPM. The average ammonia concentration remained essentially the same, 33 PPM, over the course of the night.
在图3中可以看到氨气浓度有同样的循环模式，在一个鸡群三周龄的鸡舍最低通风扇每隔5分钟运转90秒。最低风扇运转降低氨浓度大约7ppm，但是到最低换气扇“非周期”结束时又回到7ppm。夜里平均氨浓度基本保持在33ppm不变。
Figure 3. Ammonia concentration in broiler house with three-week-old birds
For any minimum ventilation fan setting the ammonia levels will tend to reach a level of equilibrium. In Figures 1, 2, and 3, though the minimum ventilation fans reduced ammonia concentrations quickly, the reduction was temporary and over the short term average ammonia levels did not significantly change. The equilibrium ammonia concentration can of course be lowered by increasing the minimum ventilation rate.
对于任何最低通风风扇设置，氨气水平均趋于达到平衡水平。在图1、图2和3中，虽然最小换气扇迅速降低了氨浓度，但这种减少是暂时的，在短期，平均氨水平没有显著变化。当然，平衡氨浓度可以通过提高最小通风量而得到降低。
An important fact to keep in mind is that the reduction in the equilibrium or “average” ammonia concentration will be roughly proportional to the change in exhaust fan runtime.
This means that in order to make large changes in average ammonia concentrations, relatively large changes in minimum ventilation fan runtime need to be made. For instance, the minimum ventilation fan runtime in the house illustrated in Figure 3 was increased from 90 seconds to 120 seconds out of five minutes (4:00 am). 要记住的一个重要事实是，在平衡或“平均”氨浓度的降低与排气扇运行时间的变化是大致成比例的。这意味着，为了让平均氨浓度出现大的改变，最低通风风扇运行时间需要进行相当大的变化。例如，将图3所示的鸡舍内最低通风扇运行时间从每5分钟90秒升至120秒（上午04点）。 The increase in fan runtime of 25% reduced average ammonia concentration by 22% (from 33 to 27 PPM) (Figure 4). Increasing fan runtime from 90 to 150 seconds, a 40% increase, reduced ammonia concentration by 35% (from 33 PPM to 22 PPM) (Figure 5). So in short, if you want to cut your ammonia levels in half, double your minimum ventilation rate. This holds true if the ammonia concentration is 80 PPM and you want to drop it to 40 PPM or even if the ammonia concentration is 40 PPM and you want to decrease it to 20 PPM.
风扇运行时间增长25％，平均氨气浓度降低22％（从33降至27ppm；图4）。将风扇运转时间从90秒增加到150秒时，即增加40％，氨气浓度降低35％（从33ppm降至22ppm；图5）。 简而言之,如果你想减少一半的氨水平，那么最低通风速率加倍。这在氨浓度为80 ppm你想把它降低至40 ppm或氨浓度为40 ppm你想降至20 ppm时有效。
Figure 4. Increasing minimum ventilation fan runtime from 90 to 120 seconds out of five minutes (4:05 am)
Figure 5. Increasing minimum ventilation fan runtime from 90, to 120 (4:05 am), then to 150 seconds out of five minutes (4:50 am)
Does this mean that if you have high ammonia concentrations that you may have to double or quadruple your minimum ventilation rates indefinitely? Not necessarily. Though high minimum ventilation rates will help to keep ammonia levels to a minimum they will also tend to address the root cause of ammonia: litter moisture. Over time, higher ventilation rates will tend to reduce litter moisture levels, which in turn will reduce the ammonia generation rate, which in turn leads to lower ammonia levels and an overall reduction in the minimum ventilation rate required to keep ammonia concentrations to a reasonable level.
这是否意味着如果氨浓度高时，你就得无限地增加最低通风率？不一定。尽管较高的最低通风率有助于保持氨水平处于最低，但还是要解决生成氨气的根源:垫料水分。 随着时间的推移,较高的通风率往往会降低垫料中的水分含量，从而降低氨的产生率，进而导致氨水平较低以及需要最低通风率全面降低来保持氨浓度到合理的水平。 Can this method of ammonia control prove expensive? Sure. But, the fact is that once you have an ammonia problem it is expensive to solve. The key to keeping ammonia levels and heating costs to a minimum is preventing high ammonia levels in the first place. Between flocks remove cake from the house as soon as the birds leave and ventilate the house to help dry the litter. Use a litter treatment according to manufacturer’s recommendations prior to chick placement. Most importantly closely manage house moisture levels by monitoring the relative humidity of the air in the house. The relative humidity of the air in a house is an indirect measure of litter moisture. Generally speaking, the ideal relative humidity would be approximately 50%. As the relative humidity of the air in the house climbs, so does litter moisture. Increased levels of litter moisture results in higher ammonia production rates. If you allow the average relative humidity climb to 70 to 80% you will have wet litter and high ammonia levels which can only be reduced to acceptable levels by a dramatic increase in minimum ventilation rates. To avoid this situation, make relatively small adjustments to the minimum ventilation rates on a daily basis. Record the relative humidity in your houses each morning. If you see the relative humidity climbing, make larger increases. Bottom line: don’t wait until you have an ammonia problem to try to solve it. After all, “an ounce of prevention is worth a pound of cure.”
这种方法控制氨气水品很贵吗？当然。但是，事实是一旦出现氨气问题，那么解决起来会更贵的。保持氨气水平和供热成本降到最低的关键是将预防高氨气水平放在首位。在空栏期一但出栏，立即将鸡舍内结块的垫料清除并且给鸡舍通风以干燥垫料。按照生产商的建议在进鸡之前进行垫料处理。 最重要的是，通过监测空气的相对湿度紧密管理鸡舍内的湿度。鸡舍内空气的相对湿度是一种间接测量垫料水分的方法。一般来说，理想的相对湿度约50%。随着空气相对湿度增加垫料水分也相应增加。垫料水分含量增加会导致氨生产速率增加。 如果空气平均相对湿度升至70-80%，那么垫料会潮湿，氨气水平也很高，这只能通过大幅提高最低通风速率来将其降低至可接受水平。 底线：不要等到问题出现才来想办法解决。毕竟，“一盎司的预防胜过一磅治疗”。 |
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